94th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (August 10, 2022) Material 1
Effective reproduction number: On a national basis, the most recent number is above 1 (1.03 as of July 24), while the figure stands at 1.01 in the Tokyo metropolitan area and 1.03 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on the reporting dates.
The number of new cases of infection was approximately 865 (roughly 1021 in Sapporo City), with a ratio to the previous week of 1.15. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 30%.
In Ibaraki, Tochigi, and Gunma, the numbers of new cases of infection were roughly 982, 912, and 885, with ratios to the previous week of 1.25, 1.05, and 1.09, respectively. In Ibaraki, Tochigi, and Gunma, they were mainly in their 30s or younger. The use rates of beds are slightly more than 60% in Ibaraki, approximately 60% in Tochigi, and slightly less than 60% in Gunma.
The number of new cases of infection in Tokyo was approximately 1,540, with a ratio to the previous week of 0.97. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 50%, while the use rate of beds for severe cases is slightly more than 60%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection were roughly 1,135, 1,038, and 1,037, with ratios to the previous week of 1.01, 1.00, and 0.94, respectively. The use rates of beds are slightly less than 70% in Saitama, slightly more than 90% in Chiba, and approximately 80% in Kanagawa.
The number of new cases of infection in Aichi was approximately 1,324, with a ratio to the previous week of 1.07. The infected individuals are mainly in their 30s or younger. The use rate of beds is approximately 80%. In Gifu, Shizuoka, and Mie, the numbers of new cases of infection were roughly 1,133, 1,106, and 1,104, with ratios to the previous week of 1.20, 1.19, and 1.17, respectively. The use rate of beds is slightly less than 60% in Gifu and Mie, and slightly more than 80% in Shizuoka.
The number of new cases of infection in Osaka was approximately 1,596, with a ratio to the previous week of 1.01. The infected individuals are mainly in their 30s or younger. The use rate of beds is approximately 70%, while the use rate of beds for severe patients is slightly more than 40%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection were roughly 1,202, 1,370, 1,347, 1,116, and 1,227, with ratios to the previous week of 1.02, 1.03, 1.09, 1.09, and 1.30, respectively. The use rates of beds are slightly more than 70% in Shiga and Wakayama, roughly 50% in Kyoto, and slightly more than 60% in Hyogo and Nara.
The number of new cases of infection in Fukuoka was approximately 1,577, with a ratio to the previous week of 0.97. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 70%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection were about 1,344, 1,302, 1,504, 1,201, 1,553, and 1,441, with ratios to the previous week of 1.04, 1.24, 1.03, 1.09, 1.15, and 1.05, respectively. The use rates of beds are roughly 50% in Saga and Oita, slightly more than 60% in Nagasaki, slightly less than 70% in Kumamoto, slightly less than 50% in Miyazaki, and slightly more than 70% in Kagoshima.
The number of new cases of infection was the highest nationwide at approximately 2,262, with a ratio to the previous week of 0.96. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 80%, while the use rate of beds for severe cases is slightly more than 30%.
Aomori, Niigata, Fukui, Shimane, Hiroshima, and Kochi had ratios to the previous week of 0.95, 1.12, 0.94, 1.16, 1.41, and 1.36, respectively. The number of new cases of infection was approximately 908 in Shimane. The use rates of beds are slightly more than 50% in Aomori, slightly more than 70% in Niigata, and slightly more than 60% in Ishikawa, Okayama, and Hiroshima.
It is thought that the infection status is affected by the following changes in factors that increase and suppress infection.
It has become clear that as a certain period elapses after the third vaccination, the infection prevention effect is attenuated, compared to the aggravation prevention effect. In addition, the immunity acquired from previous infections is expected to similarly decline in the future.
The nighttime population is flat, overall. In the Tokyo metropolitan area, Chubu area, Kansai area, and Okinawa, it has decreased or remained flat. In addition, the summer vacation at schools, etc. may have contributed to the decrease in the number of newly infected young people, mainly in their teens.
After the prevalence of BA.2 lineage, it is estimated that the BA.5 lineage will become mainstream and replace it. The BA.5 lineage is thought to increase the number of infected persons more easily, and there are concerns regarding immune escape, which may be a factor in increasing the number of infected persons.
It is a time when indoor activities increase due to rising temperatures, but ventilation may be difficult because air conditioning is prioritized.
Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, the national and local governments are required to secure a system that enables testing, and further utilize testing.
Re-inspection and implementation of the following basic infection control measures are needed.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. The death toll from the previous outbreak compared to last summer's outbreak had a higher proportion of people aged 80 and over. It is reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low from 10 days after the date of onset, and that no shedding is observed after 8 days from the date of diagnosis in those without symptoms.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination. Regarding the fourth vaccination, while the preventive effect against aggravation was not reduced for 6 weeks, the preventive effect against infection was limited, and it was reported that the effect lasted only for a short time.
Worldwide, the proportion of the BA.5 lineage is increasing, suggesting that this lineage is superior to the BA.2 lineage in terms of increasing the number of infected people. The number of positive tests is on the rise globally, as replacement by the BA.5 lineage proceeds.
The BA.5 lineage has shown a tendency to escape existing immunity compared with the BA.1 and BA.2 lineages, but no clear findings on the infectivity have been shown. The effective reproduction number of the BA.5 lineage calculated based on the data of Tokyo was about 1.27 times that of BA.2. It was also estimated that it was about 1.3 times higher in samples collected from private testing institutions nationwide.
According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.5 lineage compared to existing Omicron variants. On the other hand, the pathogenicity of the BA.5 lineage is reportedly higher than that of the BA.1 and BA.2 lineages, based on Japanese laboratory data, but it has not been confirmed clinically at this time. Although it is unknown whether it is due to the traits of the BA.5 lineage, it should be noted that the numbers of inpatient cases and severe cases are increasing in countries where the number of infected people is increasing mainly in the BA.5 lineage. According to genomic surveillance in Japan, the detection rate of the BA.5 lineage is increasing, and replacement has presumably progressed.
In addition, the BA.2.75 lineage, which has been reported mainly in India since June, has been detected in Japan. However, no clear findings have been obtained overseas regarding its infectivity or severity, compared with other lineages. It is necessary to continue to collect and analyze the situation and findings in other countries regarding these characteristics of the virus, and to continue monitoring by genome surveillance.
Figures (Number of new infections reported etc.) (PDF)
93rd Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (August 3, 2022) Material 1
Effective reproduction number: On a national basis, the most recent number is above 1 (1.17 as of July 17), while the figure stands at 1.16 in the Tokyo metropolitan area and 1.19 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection was approximately 753 (about 920 in Sapporo City), with a ratio to the previous week of 1.52. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 30%.
In Ibaraki, Tochigi, and Gunma, the numbers of new cases of infection were about 788, 871, and 814, with ratios to the previous week of 1.49, 1.28, and 1.18, respectively. In Ibaraki, Tochigi, and Gunma, they were mainly in their 30s or younger. The use rates of beds are slightly more than 40% in Ibaraki, slightly more than 50% in Tochigi, and slightly less than 50% in Gunma.
The number of new cases of infection in Tokyo was approximately 1,595, with a ratio to the previous week of 1.11. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 50%, while the use rate of beds for severe cases is slightly more than 50%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection were about 1,125, 1,039, and 1,106, with ratios to the previous week of 1.21, 1.17, and 1.26, respectively. The use rates of beds are slightly more than 60% in Saitama, slightly less than 60% in Chiba, and slightly more than 80% in Kanagawa.
The number of new cases of infection in Aichi was approximately 1,240, with a ratio to the previous week of 1.10. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 60%. In Gifu, Shizuoka, and Mie, the numbers of new cases of infection were about 947, 932, and 944, with ratios to the previous week of 1.25, 1.05, and 1.29, respectively. The use rates of beds are slightly less than 50% in Gifu, slightly more than 40% in Mie, and slightly more than 70% in Shizuoka.
The number of new cases of infection in Osaka was approximately 1,576, with a ratio to the previous week of 1.01. The infected individuals are mainly in their 30s or younger. The use rate of beds is approximately 60%, while the use rate of beds for severe cases is slightly less than 40%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection were about 1,178, 1,334, 1,238, 1,020, and 944, with ratios to the previous week of 1.64, 1.29, 1.17, 1.24, and 1.22, respectively. The use rates of beds are slightly more than 60% in Shiga, slightly less than 50% in Kyoto, approximately 60% in Hyogo, slightly less than 60% in Nara, and slightly more than 70% in Wakayama.
The number of new cases of infection in Fukuoka was approximately 1,623, with a ratio to the previous week of 1.10. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 80%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection were about 1,292, 1,053, 1,464, 1,099, 1,351, and 1,367, with ratios to the previous week of 1.05, 1.26, 1.00, 1.04, 1.23, and 1.21, respectively. The use rates of beds are slightly more than 50% in Saga and Nagasaki, slightly more than 60% in Kumamoto, approximately 50% in Oita, slightly more than 40% in Miyazaki, and slightly less than 80% in Kagoshima.
The number of new cases of infection was the highest nationwide at approximately 2,353, with a ratio of this week to last week of 1.04. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 70%, while the use rate of beds for severe cases is slightly more than 40%.
Aomori, Niigata, Fukui, Shimane, Okayama, and Hiroshima had ratios to the previous week of 0.97, 1.54, 1.61, 0.81, 1.39, and 1.35, respectively. The number of new cases of infection was approximately 785 in Shimane. The use rates of beds are slightly more than 50% in Aomori and Kochi, slightly less than 60% in Niigata, and slightly more than 60% in Hiroshima.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
It has become clear that as a certain period elapses after the third vaccination, the infection prevention effect is attenuated compared to the aggravation prevention effect. In addition, the immunity acquired from previous infections is expected to similarly decline in the future.
Although the nighttime population is overall flat, in metropolitan areas such as Tokyo, Kanagawa, Aichi, and Osaka, there are regions where the number is increasing, including the high-risk late night.
After the prevalence of BA.2 lineage, it is estimated that the BA.5 lineage will become mainstream and replace it. The BA.5 lineage is thought to increase the number of infected persons more easily, and there is concern about immune escape, which may be a factor in increasing the number of infected persons.
It is a time when indoor activities increase due to rising temperatures, but ventilation may be difficult because air conditioning is prioritized.
Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, the national and local governments are required to secure a system that enables testing, and further utilize testing.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. The death toll from the previous outbreak compared to last summer's outbreak had a higher proportion of people aged 80 and over. It is reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low from 10 days after the date of onset, and that no shedding is observed after 8 days from the date of diagnosis in those without symptoms.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination. Regarding the fourth vaccination, while the preventive effect against aggravation was not reduced for 6 weeks, the preventive effect against infection was limited, and it was reported that the effect lasted only for a short time.
Worldwide, the proportion of the BA.5 lineage is increasing, suggesting that this lineage is superior to the BA.2 lineage in terms of increasing the number of infected people. The number of positive tests is on the rise globally, as replacement by the BA.5 lineage proceeds. The BA.5 lineage has shown a tendency to escape existing immunity compared with the BA.1 and BA.2 lineages, but no clear findings on the infectivity have been shown. The effective reproduction number of the BA.5 lineage calculated based on the data of Tokyo was about 1.27 times that of BA.2. It was also estimated that it was about 1.3 times higher in samples collected from private testing institutions nationwide.
According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.5 lineage compared to existing Omicron variants. On the other hand, the pathogenicity of the BA.5 lineage is reportedly higher than that of the BA.1 and BA.2 lineages, based on Japanese laboratory data, but it has not been confirmed clinically at this time. Although it is unknown whether it is due to the traits of the BA.5 lineage, it should be noted that the numbers of inpatient cases and severe cases are increasing in countries where the number of infected people is increasing mainly in the BA.5 lineage. According to genomic surveillance in Japan, the detection rate of the BA.5 lineage is increasing, and replacement has presumably progressed.
In addition, the BA.2.75 lineage, which has been reported mainly in India since June, has been detected in Japan, but no clear findings have been obtained overseas regarding its infectivity and severity compared with other lineages. It is necessary to continue to collect and analyze the situation and findings in other countries regarding these characteristics of the virus, and to continue monitoring by genome surveillance.
Figures (Number of new infections reported etc.) (PDF)
92nd Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (July 27, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is greater than 1 (1.24, as of July 10), while the figure stands at 1.26 in both the Tokyo metropolitan and Kansai areas.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection was approximately 494 (about 569 in Sapporo City), with a ratio to the previous week of 2.29. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 20%.
In Ibaraki, Tochigi, and Gunma, the numbers of new cases of infection were about 530, 682, and 692, with ratios to the previous week of 2.08, 2.57, and 2.10, respectively. In Ibaraki, Tochigi, and Gunma, they were mainly in their 30s or younger. The use rates of beds are slightly less than 50% in Ibaraki, approximately 40% in Tochigi, and approximately 50% in Gunma.
The number of new cases of infection in Tokyo was approximately 1,438, with a ratio to the previous week of 1.79. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 40%, while the use rate of beds for severe cases is slightly more than 50%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection were about 927, 892, and 875, with ratios to the previous week of 1.78, 1.85, and 1.50, respectively. The use rates of beds are approximately 50% in Saitama, slightly more than 50% in Chiba and slightly less than 70% in Kanagawa.
The number of new cases of infection in Aichi was approximately 1,130, with a ratio to the previous week of 2.17. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 40%. In Gifu, Shizuoka, and Mie, the numbers of new cases of infection were about 758, 885, and 730, with ratios to the previous week of 2.16, 2.19, and 1.83, respectively. The use rates of beds are slightly more than 30% in Gifu, approximately 70% in Shizuoka, and slightly more than 40% in Mie.
The number of new cases of infection in Osaka was approximately 1,555, with a ratio to the previous week of 2.18. The infected individuals are mainly in their 30s or younger. The use rate of beds is approximately 50%, while the use rate of beds for severe cases is slightly less than 30%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection were about 717, 1,035, 1,060, 826, and 771, with ratios to the previous week of 1.57, 1.92, 1.91, 1.49, and 1.73, respectively. The use rates of beds are slightly more than 50% in Shiga and Hyogo, slightly more than 30% in Kyoto, slightly more than 40% in Nara, and slightly more than 60% in Wakayama.
The number of new cases of infection in Fukuoka was approximately 1,481, with a ratio to the previous week of 2.01. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 60%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection were about 1,231, 834, 1,461, 1,055, 1,097, and 1,133, with ratios to the previous week of 1.58, 2.01, 1.63, 1.73, 1.78, and 1.70, respectively. The use rates of beds are slightly more than 40% in Saga, slightly more than 50% in Nagasaki, approximately 60% in Kumamoto, slightly more than 40% in Oita, slightly less than 40% in Miyazaki, and slightly more than 60% in Kagoshima.
The number of new cases of infection was the highest nationwide at approximately 2,260, with a ratio of this week to last week of 1.46. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 80%, while the use rate of beds for severe cases is slightly more than 30%.
Miyagi, Akita, Tochigi, Niigata, Toyama, Yamanashi, Shimane, and Kagawa had ratios to the previous week of 2.85, 2.67, 2.57, 2.35, 2.61, 2.38, 1.18, and 2.11, respectively. The number of new cases of infection was approximately 969 in Shimane. The use rates of beds are approximately 60% in Aomori, approximately 50% in Fukushima and Hiroshima, and slightly more than 50% in Ishikawa.
The number of new cases has again hit a record high nationwide, and all prefectures have greatly exceeded the previous spread of infection as the rapid spread of infection continues. The infection level in Okinawa continues to be higher than in other regions, and the highest so far, while the use rate of beds is also severe. In addition, the rapid increase in cases of infection and close contact are having an impact on social activities overall.
The number of new cases of infection by age group is increasing nationwide in all age groups, including the elderly. In the past, increase in the number of severe cases and deaths has tended to lag behind a rapid increase in the number of new infections, and there are concerns about these increases as the number of infected elderly people increases.
Regarding the future infection situation, the epi curve of the onset date and short-term forecasts in large cities predict that the number of new infections will continue to increase or at best level off in many regions and will reach record highs nationwide. Close attention should be paid to the medical care provision system, with the utmost caution.
Factors in the continued increase in the number of infected individuals include (1) the gradual diminishing of the immunity acquired by the third vaccination and infection, (2) the increased contact that is expected due to the influence of summer vacation etc., and (3) the presumed replacement of the Omicron variant by lineages such as BA.5.
Regarding the places of infection of new cases, there is an increasing trend at home and a decreasing trend at schools (it must be kept in mind active epidemiological surveillance is focused on large cities, and that infection routes are not fully understood).
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
It has become clear that as a certain period elapses after the third vaccination, the infection prevention effect is attenuated compared to the aggravation prevention effect. In addition, the immunity acquired from previous infections is expected to similarly decline in the future.
The nighttime population is decreasing in many regions, including large cities such as Tokyo, Aichi, and Osaka. However, in some areas the number of infections has leveled off or turned to increase.
After the prevalence of BA.2 lineage, it is estimated that the BA.5 lineage will become mainstream and replace it. In particular, the BA.5 lineage is thought to increase the number of infected persons more easily, and there is concern about immune escape, which may be a factor in increasing the number of infected persons.
It is a time when indoor activities increase due to rising temperatures, but ventilation may be difficult because air conditioning is prioritized.
Nationwide, the burden on the outpatient examination system is increasing, and although there are regional differences in the use rate of beds, it has risen to 30% in most regions, including large cities, due to the increase in the number of new infections, and the number of regions exceeding 50% is also increasing. In addition, the numbers of home care recipients and medical treatment adjustments are increasing in most regions and are rapidly increasing in some regions.
Especially in Okinawa, the use rate of beds continues to rise, exceeding 80%, and the situation is severe, and nationwide, the increasing number of infections among healthcare workers is placing a burden on the medical care provision system. In the field of nursing care also, the difficult situation continues due to the increasing numbers of patients being treated in facilities and of infections among workers.
The positive rate of the test has increased, and there is concern whether the test is being appropriately received by those who need it, such as people with symptoms.
Cases of difficult emergency transportation continue to increase rapidly nationwide for both suspected non-COVID-19 cases and suspected COVID-19 cases, although there are regional differences. In addition, careful attention should be paid to the increase in ambulance transportation due to heat stroke.
In the midst of rapid spread of infection, it is necessary to reduce as much as possible the chances of contacts which risk infection, based on the various knowledge that Japanese society has already learned. Also, in order to maintain socio-economic activities, it is necessary to work on methods for people to avoid infecting and being infected.
To this end, the national and local governments will remind the public of the need for routine infection control measures and take measures to support the public's efforts to prevent infection. It is also necessary to make further efforts to strengthen the medical care provision system.
Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, the national and local governments are required to secure a system that enables testing, and further utilize testing.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. The death toll from the previous outbreak compared to last summer's outbreak had a higher proportion of people aged 80 and over. It is reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low from 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur from 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination. Regarding the fourth vaccination, while the preventive effect against aggravation was not reduced for 6 weeks, the preventive effect against infection was limited, and it was reported that the effect lasted only for a short time.
Worldwide, the proportion of the BA.5 lineage is increasing, suggesting that this lineage is superior to the BA.2 lineage in terms of increasing the number of infected people. The number of positive tests is on the rise globally, as replacement by the BA.5 lineage proceeds. The BA.5 lineage has shown a tendency to escape existing immunity compared with the BA.1 and BA.2 lineages, but no clear findings on the infectivity have been shown. The effective reproduction number of the BA.5 lineage calculated based on the data of Tokyo was about 1.27 times that of BA.2. It was also estimated that it was about 1.3 times higher in samples collected from private testing institutions nationwide.
According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.5 lineage compared to existing Omicron variants. On the other hand, the pathogenicity of the BA.5 lineage is reportedly higher than that of the BA.1 and BA.2 lineages, based on Japanese laboratory data, but it has not been confirmed clinically at this time. Although it is unknown whether it is due to the traits of the BA.5 lineage, it should be noted that the numbers of inpatient cases and severe cases are increasing in countries where the number of infected people is increasing mainly in the BA.5 lineage.
The BA.5 lineage has been detected both in Japan and in quarantine. According to genomic surveillance, the detection rate of the BA.5 lineage is increasing, and replacement has presumably progressed. It is necessary to continue to collect and analyze the situation and findings in other countries regarding the characteristics of the virus, and to continue monitoring by genome surveillance.
Figures (Number of new infections reported etc.) (PDF)
90th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (July 13, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is above 1 (1.14 as of June 26), while the figure stands at 1.19 in the Tokyo metropolitan area and 1.16 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection was approximately 111 (about 135 in Sapporo City), with a ratio to the previous week of 1.37. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 10%.
In Ibaraki, Tochigi, and Gunma, the numbers of new cases of infection were about 118, 122, and 160, with ratios to the previous week of 2.05, 2.58, and 2.70, respectively. In Ibaraki and Tochigi, they were mainly in their 30s or younger, and in Gunma, mainly in their 20s or younger. The use rates of beds are slightly more than 10% in Ibaraki and Gunma, and approximately 10% in Tochigi.
The number of new cases of infection in Tokyo was approximately 446, with a ratio to the previous week of 2.37. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 20%, and the use rate of beds for severe cases is slightly more than 30%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection were about 232, 246, and 296, with ratios to the previous week of 2.19, 2.33, and 2.41, respectively. The use rates of beds are slightly more than 20% in Saitama, Chiba, and Kanagawa.
The number of new cases of infection in Aichi was approximately 294, with a ratio to the previous week of 2.26. The individuals are mainly in their 20s or younger. The use rate of beds is slightly less than 20%. In Gifu, Shizuoka, and Mie, the numbers of new cases of infection were about 235, 212, and 224, with ratios to the previous week of 2.18, 2.65, and 2.07, respectively. The use rates of beds are slightly less than 20% in Gifu and Shizuoka, and approximately 30% in Mie.
The number of new cases of infection in Osaka was approximately 421, with a ratio to the previous week of 2.22. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 20%, and the use rate of beds for severe cases is slightly less than 10%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection were about 243, 284, 276, 250, and 306, with ratios to the previous week of 2.29, 2.27, 2.13, 3.01, and 2.09, respectively. The use rates of beds are approximately 20% in Kyoto, slightly more than 40% in Wakayama and Shiga, slightly less than 30% in Hyogo, and slightly more than 10% in Nara.
The number of new cases of infection in Fukuoka was approximately 406, with a ratio to the previous week of 2.27. The individuals are mainly in their 20s or younger. The use rate of beds is slightly more than 20%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection were about 626, 298, 640, 402, 379, and 409, with ratios to the previous week of 2.00, 1.58, 1.75, 2.24, 2.24, and 1.97, respectively. The use rates of beds are approximately 30% in Saga, slightly more than 20% in Nagasaki, slightly less than 50% in Kumamoto, approximately 30% in Oita, slightly more than 30% in Kagoshima, and approximately 20% in Miyazaki.
The number of new cases of infection was the highest nationwide at approximately 1,118, with a ratio of this week to last week of 1.52. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 50%, while the use rate of beds for severe cases is slightly more than 20%.
In Iwate, Akita, Yamanashi, Nagano, Tottori, and Shimane, the ratio to the previous week was 2.77, 3.57, 2.61, 2.58, 2.18, and 1.80, respectively, and the number of new cases of infection in Shimane was about 776. The use rates of beds are slightly less than 30% in Aomori, slightly more than 20% in Fukushima, and slightly more than 30% in Shimane.
The number of new cases of infection is increasing in all prefectures, and in many areas the increase is large and the infection is spreading rapidly. In addition, Okinawa continues to have a higher level of infection than other areas, and is now the highest level to date.
The number of new cases of infection by age group increased in all age groups, and the rate of increase was particularly large among those in their 50s or younger.
Regarding the places of infection of new cases, the proportion at schools and at home are increasing (it must be kept in mind active epidemiological surveys are focused on large cities, and that infection routes are not fully understood). In Tokyo, an increase in infections at places of eating, drinking, and work has also been reported.
Regarding future infection status, the number of new infections is expected to continue to increase in many regions, based on the epi-curve of the date of onset and short-term forecast in large cities. Since (1) the immunity acquired by the third vaccination and infection is gradually decreasing, (2) an increase in contact is expected due to the influence of three consecutive holidays and summer vacation, and (3) replacement of the Omicron variant by lineages such as BA.5 is proceeding, there is concern that the number of infects will continue to increase rapidly, and it will be necessary to pay close attention to the impact on the medical care provision system.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
The third vaccination is proceeding, but it should be noted that as a certain period elapses after the third vaccination, it is expected that the infection prevention effect will be weakened compared to the aggravation prevention effect. In addition, the immunity acquired from previous infections is expected to similarly decline in the future.
Although the nighttime population is decreasing in some regions, it shows an increasing trend in many areas, mainly in large cites. Since in some areas the number approaches or exceeds the peak at the end of last year, it is necessary to pay attention to the impact on the infection status.
After the prevalence of BA.2 lineage, the replacement by BA.5 lineage is progressing. In particular, the BA.5 lineage is thought to increase the number of infected persons more easily, and there is concern about immune escape, which may be a factor in increasing the number of infected persons.
It is a time when indoor activities increase due to rising temperatures, but ventilation may be difficult because air conditioning is prioritized.
Nationwide, the use rate of beds is generally low, but as the number of newly infected individuals increases, it has been on an upward trend in some areas, including large cities. Especially in Okinawa, the use rate of beds tends to be higher than in the country as a whole.
In cases of difficult emergency transportation, there is an increasing trend nationwide for both suspected non-COVID-19 cases and suspected COVID-19 cases. In addition, careful attention should be paid to the increase in ambulance transportation due to heat stroke.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
The number of new cases of infection is increasing in all prefectures, and local governments need to continue to inspect and strengthen their testing, health, and medical care provision systems.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Infection control measures including active promotion of vaccinations for teachers and nursery teachers will be thoroughly implemented, as well as infection control measures for children, while sharing situations where the risk of infection in children and students increases with staff, children, parents, etc. It is also necessary to continue educational activities and social functions as far as possible. It is important to establish an environment where children and workers can take a leave of absence, in the case of any poor health conditions. At the same time, thorough infection control measures are also required at home. Masks are not recommended for children under 2 years of age, and for preschool children over 2 years of age, there are concerns about the risk of heat stroke and the effects of difficulty in seeing facial expressions. Therefore, it is necessary to thoroughly inform nursery schools, etc. that masks are not uniformly required, and that children should not be forced to wear them. Schools must be thoroughly informed that it is not necessary to wear a mask during physical education classes, athletic club activities, or when going to and from school.
Thorough measures are needed to control infections in the elderly. Therefore, workers are actively examined. In order to prevent aggravation, the fourth vaccination of residents will proceed. Further, it is important to secure external support systems for infection control and medical care at facilities, and to promptly intervene when infection is confirmed at facilities.
In order to maintain social functions, in addition to reinspection and utilization of business continuity plans, efforts are required to utilize telework and promote the taking of time off. In addition, thorough health management of employees, including the use of apps, and securing an environment where they can take a leave of absence if they are even a little unwell are necessary. In addition, a third vaccination in the workplace should be actively promoted.
The number of new cases of infections is increasing in all prefectures. The number of contacts is expected to increase due to the three consecutive holidays and summer vacation. For this reason, in order to minimize the increase in the number of cases of infection, it is necessary to thoroughly implement basic infection control measures and daily health management, and cooperate in efforts to reduce the risk of infection.
In preparation for the spread of infection, a fourth vaccination is recommended for the elderly and those at risk of severe illness. It is important for people to receive the third vaccination, regardless of type. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, but also in younger persons, in order to protect their health. It is important to consider vaccination again for people who have not received the first or second vaccination.
As basic infection control measures, it is necessary to continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking. On the other hand, the use of a mask is not necessary outdoors, except when talking at a close distance. Especially in summer, removing the mask outdoors is recommended from the viewpoint of preventing heat stroke.
It is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. Particularly, if there is a chance of meeting people at high risk of severe illness, such as the elderly, it is necessary to check the condition before visiting, and also to recommend a preliminary test using an antigen test kit, etc.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. It has been reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Worldwide, the proportions of the BA.4 and BA.5 lineage are increasing, suggesting that these lineages are superior to the BA.2 lineage in terms of increasing the number of infected people. The number of positive tests is on the rise globally, as replacement by the BA.4 and BA.5 lineages proceeds. The effective reproduction number of the BA.5 lineage calculated based on the data of Tokyo was about 1.27 times that of BA.2.
According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.4 and BA.5 lineages compared to existing Omicron variants. On the other hand, the pathogenicity of the BA.5 lineage is reportedly higher than that of the BA.1 and BA.2 lineages, based on Japanese laboratory data, but it has not been confirmed clinically at this time. It should be noted that the numbers of inpatient cases and severe cases are increasing in countries where the number of infected people is increasing mainly in BA.4 and BA.5 lineages.
The BA.4 lineage and BA.5 lineage have both been detected in Japan and in quarantine. According to genomic surveillance, the BA.2 lineage continues to be the mainstream in Japan, but the detection rate of the BA.5 lineage is increasing, and replacement is progressing. It is necessary to continue to collect and analyze the situation and findings in other countries regarding the characteristics of the virus, and to continue monitoring by genome surveillance.
Figures (Number of new infections reported etc.) (PDF)
89th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (June 30, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is below 1, at 0.98 (as of June 12). The figure stands at 1.02 in the Tokyo metropolitan area and 0.97 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 77 (roughly 85 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.85). The infected individuals are mainly in their 30s or younger. The number leveled off in those in their 70s, and decreased slightly or decreased in other age groups. The use rate of beds is slightly less than 10%.
In Ibaraki, the number of new cases of infection is approximately 52, with a ratio of this week to last week of more than 1 (1.01). The individuals are mainly in their 20s or younger. The number slightly increased in those in their teens and 20s, slightly increased in the 40s and 50s, and decreased slightly or decreased in other age groups. The use rate of beds is slightly less than 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 30 and 34, respectively, with a ratio of this week to last week of less than 1 (0.85 and 0.72). The use rates of beds are slightly less than 10% in Gunma and less than 10% in Tochigi.
In Tokyo, the number of new cases of infection is approximately 118, with a ratio to the previous week of more than 1 (1.37). The infected individuals are mainly in their 30s or younger. It has increased or slightly increased in all age groups. The use rate of beds is slightly more than 10%, and the use rate of beds for severe patients is slightly more than 10%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 65, 63, and 77, respectively, with a ratio of this week to last week of more than 1 (1.13, 1.27, and 1.25). The use rate of beds is approximately 10% in Saitama, and slightly less than 10% in Chiba and Kanagawa.
In Aichi, the number of new cases of infection is approximately 88, with a ratio of this week to last week of more than 1 (1.21). The individuals are mainly in their 20s or younger. It has increased or slightly increased in all age groups. The use rate of beds is slightly less than 10%. In Gifu, Shizuoka and Mie, the ratios of this week to last week are more than 1 (1.21, 1.29, and 1.29, respectively), with the number of new cases of infection at approximately 75, 54, and 75. The use rates of beds are slightly less than 10% in Gifu, less than 10% in Shizuoka, and slightly more than 10% in Mie.
In Osaka, the number of new cases of infection is approximately 117, with a ratio of this week to last week of more than 1 (1.33). The individuals are mainly in their 20s or younger. The number leveled off in those in their 80s and older and increased slightly or increased in other age groups. The use rate of beds is slightly more than 10%, and the use rate of beds for severe cases is slightly less than 10%. In Kyoto, Hyogo and Wakayama,, the numbers of new cases of infection are 82, 86, and 77, respectively, with a ratio to that for the previous week of more than 1 (1.04, 1.21, and 1.53). In Shiga and Nara, the numbers of new cases of infection are approximately 75 and 54, with a ratio of this week to last week of less than 1 (0.98 and 0.97). The use rates of beds is slightly more than 10% in Kyoto, approximately 10% in Wakayama, slightly less than 10% in Shiga and Hyogo, and less than 10% in Nara.
In Fukuoka, the number of new cases of infection is approximately 110, with a ratio of this week to last week of more than 1 (1.20). The infected individuals are mainly in their 30s or younger. It has increased or slightly increased in all age groups. The use rate of beds is approximately 10%. In Saga, Nagasaki, Kumamoto, Oita, and Miyazaki, the numbers of new cases of infection are 187, 137, 227, 84, and 147, respectively, with a ratio of this week to last week of more than 1 (1.42, 1.16, 1.39, 1.34, and 1.53, respectively). In Kagoshima, the number of new cases of infection is approximately 148, with a ratio of this week to last week of less than 1 (0.99). The use rates of beds are slightly more than 10% in Saga, approximately 10% in Nagasaki, slightly more than 20% in Kumamoto, less than 10% in Oita and Miyazaki, and slightly more than 20% in Kagoshima.
The number of new cases of infection is the highest nationwide, at 650, with a ratio of this week to last week of more than 1 (1.15). The infected individuals are mainly in their 30s or younger. The number leveled off in those in their 60s, but increased in other age groups. In particular, the increase among those in their teens or younger is marked. The use rate of beds is approximately 40%, while the use rate of beds for severe cases is slightly less than 20%.
In Aomori, Shimane, Hiroshima, Yamaguchi, Ehime, and Kochi, the numbers of new cases of infection are approximately 129, 195, 82, 80, 107, and 111, respectively. The use rates of beds are slightly more than 20% in Aomori, and slightly more than 10% in Shimane, Hiroshima, Yamaguchi, Ehime, and Kochi.
The number of newly infected individuals has turned upward nationwide (29 prefectures have a ratio to the previous week exceeding 1). By region, although still decreasing in some regions (decreased in 18 prefectures), the level generally showed an increasing trend in large cities. In some areas, the rate of increase is high. Okinawa has a higher level of infection than other regions and is on an upward trend, so it is necessary to pay particular attention to future trends in infection status.
The number of new cases of infection by age group slightly increased in almost all age groups nationwide. In addition, the increase in those in their 20s is large in Tokyo. In Okinawa, the number is increasing in all age groups, but as it is increasing even in the elderly, it is necessary to pay close attention to the infection situation.
The proportion of new cases of infection at schools continues to decrease, but the proportion remains high. In addition, the proportion at home is decreasing.
Regarding the future infection situation, the number of new cases of infection is expected to increase in large cities; (1) the immunity acquired by the third vaccination and infection will gradually decrease, (2) an increase in contact is expected after July due to the influence of after the rainy season, three consecutive holidays and summer vacation, and (3) since there is a possibility that the Omicron variant will be replaced by a new lineage, it will be necessary to pay close attention to the impact on the medical care provision system.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
The nighttime population is showing an increasing trend in many regions, mainly in large cites. Since in some areas the number approaches or exceeds the peak at the end of last year, it is necessary to pay attention to the impact on the infection status.
The BA.1 lineage has been replaced by the BA.2 lineage, but the new lineages BA.2.12.1, BA.4, and BA.5 lineages have been detected in Japan. In particular, the BA.5 lineage may become the mainstream lineage in Japan in the future, and could be a factor in increasing the number of infected people.
The third vaccination is proceeding, but it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the immunity acquired from previous infections is expected to gradually decline in the future.
It is a time when indoor activities increase due to rising temperatures, but ventilation may be difficult because air conditioning is prioritized.
Nationwide, the use rate of beds is generally low, but as the number of newly infected individuals begins to rise, it has stopped decreasing in large cities. In Okinawa, the number of inpatients and the use rate of beds has leveled off or slightly increased, and the use rate of beds for severe cases is also increasing.
In cases of difficult emergency transportation, recently there is an increasing trend nationwide for both suspected non-COVID-19 cases and suspected COVID-19 cases. In addition, it is expected that the number of emergency transports due to heat stroke will increase, so careful attention should be paid.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
The number of new cases of infection is on the rise nationwide, and it is necessary for local governments to inspect the medical care/testing system and public health center system.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Nationwide, the number of new cases of infection has started to increase. The number of contacts is expected to increase due to the three consecutive holidays and summer vacation. For this reason, in order to minimize the increase in the number of cases of infection, it is necessary to thoroughly implement basic infection control measures and daily health management and cooperate in efforts to reduce the risk of infection.
In preparation for the spread of infection, a fourth vaccination is recommended for the elderly and those at risk of severe illness. It is important for people to receive the third vaccination, regardless of type. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, but also in younger persons, in order to protect their health. It is important to consider vaccination again for people who have not received the first or second vaccination.
As basic infection control measures, it is necessary to continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking. On the other hand, the use of a mask is not necessary outdoors, except when talking at a close distance. Especially in summer, removing the mask outdoors is recommended from the viewpoint of preventing heat stroke.
It is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. It has been reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Currently, the BA.2 lineage remains the mainstream in Japan. Worldwide, the proportions of the BA.4 and BA.5 lineage are increasing, suggesting that these lineages are superior to the BA.2 lineage in terms of increasing the number of infected people. The number of positive tests is on the rise globally, as replacement by the BA.4 and BA.5 lineages proceeds. However, there are no clear findings on the infectivity of the BA.4 and BA.5 lineages.
According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.4 and BA.5 lineages compared to existing Omicron variants.
The BA.4 lineage and BA.5 lineage have both been detected in Japan and in quarantine. According to genomic surveillance, the BA.2 lineage continues to be the mainstream in Japan, but the detection rates of the BA.4 and BA.5 lineages may increase in the future. It is necessary to continue to collect and analyze the situation and findings in other countries regarding the characteristics of the virus, and to continue monitoring by genome surveillance.
Figures (Number of new infections reported etc.) (PDF)
88th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (June 23, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is below 1, at 0.94 (as of June 5). The figure stands at 0.93 in the Tokyo metropolitan area and 0.95 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 90 (roughly 104 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.82). The infected individuals are mainly in their 30s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is slightly less than 10%.
In Ibaraki, the number of new cases of infection is approximately 51, with a ratio of this week to last week of more than 1 (1.08). The infected individuals are mainly in their 30s or younger. It slightly decreased among those in their 20s, 50s, and 70s, while it slightly increased or increased in other age groups. The use rate of beds is less than 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 35 and 47, respectively, with a ratio of this week to last week of less than 1 (0.95 and 0.93). The use rate of beds is slightly less than 10% in Tochigi and Gunma.
In Tokyo, the number of new cases of infection is approximately 86, with a ratio to the previous week of more than 1 (1.09). The infected individuals are mainly in their 30s or younger. It has slightly decreased or slightly increased in all age groups. The use rate of beds is slightly less than 10%, while the use rate of beds for severe cases is approximately 10%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 58, 50, and 61, respectively, with a ratio of this week to last week of more than 1 (1.09, 1.08, and 1.12). The use rates of beds are approximately 10% in Saitama, less than 10% in Chiba and slightly less than 10% in Kanagawa.
In Aichi, the number of new cases of infection is approximately 73, with a ratio of this week to last week of less than 1 (0.95). The individuals are mainly in their 20s or younger. The number slightly increased in those in their 70s, and decreased slightly or decreased in other age groups. The use rate of beds is less than 10%. In Gifu and Shizuoka, he number of new cases of infection is approximately 62 and 42, respectively, with a ratio to the previous week of less than 1 (0.69 and 0.75). In Mie, the number of new cases of infection is approximately 58, with a ratio of this week to last week of more than 1 (1.04). The use rates of beds are slightly more than 10% in Gifu, less than 10% in Shizuoka, and approximately 10% in Mie.
In Osaka, the number of new cases of infection is approximately 88, with a ratio of this week to last week of less than 1 (0.93). The individuals are mainly in their 20s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is slightly more than 10%, and the use rate of beds for severe cases is slightly less than 10%. In Hyogo and Nara, the number of new cases of infection was approximately 71 and 56, respectively, with a ratio to the previous week of less than 1 (0.94 and 0.92). In Kyoto, the number of new cases of infection is approximately 79, with a ratio of this week to last week of 1.0. In Shiga and Wakayama, the numbers of new cases of infection are 76 and 50, respectively, with a ratio of this week to last week of more than 1 (1.05 and 1.01). The use rates of beds are slightly less than 10% in Shiga and Wakayama, less than 10% in Kyoto, approximately 10% in Hyogo, and slightly more than 20% in Nara.
In Fukuoka, the number of new cases of infection is approximately 92, with a ratio of this week to last week of less than 1 (0.99). The individuals are mainly in their 20s or younger. The number slightly increased in those in their 60s, and decreased slightly or decreased in other age groups. The use rate of beds is approximately 10%. In Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection are approximately 62, 96, and 149, respectively, with a ratio of this week to last week of less than 1 (0.87, 0.92, and 0.95). In Saga, Nagasaki, and Kumamoto, the numbers of new cases of infection are 131, 118, and 163, respectively, with a ratio of this week to last week of more than 1 (1.09, 1.08, and 1.12). The use rates of beds are slightly less than 10% in Saga and Oita, approximately 10% in Nagasaki, slightly more than 20% in Kumamoto, less than 10% in Miyazaki, and slightly more than 10% in Kagoshima.
The number of new cases of infection is the highest nationwide, at approximately 567, with a ratio of this week to last week of less than 1 (0.98). The infected individuals are mainly in their 30s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is approximately 40%, and the use rate of beds for severe cases is approximately 10%.
In Aomori, Shimane, Hiroshima, Yamaguchi, Ehime, and Kochi the numbers of new cases, of infection are approximately 119, 67, 84, 62, 72, and 101, respectively. The use rates of beds are slightly more than 20% in Aomori, and slightly more than 10% in Shimane, Hiroshima, Yamaguchi, Ehime, and Kochi.
The number of new infections continued to decrease nationwide except in some regions, but the decrease is slowing down. By region, there are differences in the status of infection, with decrease continuing in some regions, and some showing signs of leveling off or increasing. In particular, in some small-population areas, the number of newly infected people is surging due to clusters of outbreak. In Okinawa, the decreasing trend in the number of infected people has continued, despite repeatedly leveling off or slightly increasing, but it has been increasing for the past few days, and the number of infected people per population continues to be higher than in other areas. Therefore, it is necessary to pay particular attention to future trends in infection status.
The number of new cases of infection by age group has continued to decrease or decrease slightly in all age groups nationwide, and a similar trend seen by region, although there are regions where increases can be seen at some ages.
The proportion of new cases of infection at schools is decreasing, but the proportion remains high. In addition, in the last few days, the proportion in nursery schools, etc. has been on the rise.
Regarding the future infection situation, although short-term forecasts for large cities do not anticipate a sharp increase, (1) the immunity acquired by the third vaccination and infection will gradually decrease, (2) an increase in contact is expected after July due to the influence of after the rainy season, three consecutive holidays and summer vacation, and (3) since there is a possibility that the Omicron variant will be replaced by a new lineage, it will be necessary to pay close attention to the impact on the medical care provision system.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
The nighttime population increases or decreases each week in some regions, while in other regions the number increases continuously. Since in some areas the number approaches or exceeds the peak at the end of last year, it is necessary to pay attention to the impact on the infection status.
The replacement by the BA.2 lineage has largely occurred and compared to the time when the BA.1 lineage was dominant, it may be a factor in a slowdown in the decrease. In addition, the BA.2.12.1 lineage, BA.4 linage, and BA.5 lineage have been detected in Japan, and it is necessary to continue monitoring.
The third vaccination is proceeding, but it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the immunity acquired from previous infections is expected to gradually decline in the future.
When the temperature rises, it becomes easier to ventilate, due to climate conditions. However, elevated temperatures and rainfall may increase indoor activities.
In Okinawa, the number of inpatients and the use rate of beds has leveled off or slightly increased, but the use rate of beds for severe cases is generally decreasing. Nationwide, due to the decreasing number of new cases, the use rate of beds has continued to decline, except in some regions.
In cases of difficult emergency transportation, the numbers are decreasing nationwide for both suspected non-COVID-19 cases and suspected COVID-19 cases.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Although the number of new infections continues to decrease nationwide, the level of infection remains high, and in some areas it has leveled off or is showing signs of increase. For this reason, it is necessary to thoroughly implement basic infection control measures and daily health management, and cooperate in efforts to reduce the risk of infection.
It is important for people to receive a third vaccination as soon as possible, regardless of type, once such vaccination becomes available. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health. It is also important to consider vaccination again for people who have not received the first or second vaccination.
As basic infection control measures, it is necessary to continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking. On the other hand, the use of a mask is not necessary outdoors, except when talking at a close distance. Especially in summer, removing the mask outdoors is recommended from the viewpoint of preventing heat stroke.
It is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. It has been reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Currently, the BA.1 lineage has been largely replaced by the BA.2 lineage. Worldwide, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. It has also been reported that, when comparing the severity of the BA.1 lineage and the BA.2 lineage, there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages.
Worldwide, the proportions of the BA.2.12.1 lineage, BA.4 lineage, and BA.5 lineage are increasing, suggesting that these lineages are superior to the BA.2 lineage in terms of increasing the number of infected people.
BA.2.12.1, BA.4, and BA.5 lineages:According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.2.12.1, BA.4, and BA.5 lineages compared to existing Omicron variant. The detection rates of the BA.4 and BA.5 lineages have increased in some countries and regions, and replacement of the BA.2 lineage is progressing.
XE lineage (recombinant of BA.1 and BA.2 lineages):The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage, but the number of infected people in the world continues to decrease.
The BA.2.12.1 lineage, BA.4 lineage, BA.5 lineage, and XE lineage have all been detected in quarantine. According to genomic surveillance, the BA.2 lineage continues to be the mainstream in Japan, but the detection rates of the BA.2.12.1 lineage, BA.4 lineage, and BA.5 lineage may increase in the future. It is necessary to continue to collect and analyze the situation and findings in other countries regarding the characteristics of the virus, and to continue monitoring by genome surveillance.
Figures (Number of new infections reported etc.) (PDF)
87th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (June 8, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is less than 1 (0.91, as of May 22), and the figure stands at 0.92 in both the Tokyo metropolitan and Kansai areas.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 127 (roughly 140 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.65). The infected individuals are mainly in their 30s or younger. It decreased in all age groups. The use rate of beds is slightly more than 10%.
In Ibaraki, the number of new cases of infection is approximately 56, with a ratio of numbers for this week to last week of less than 1 (0.66). The infected individuals are mainly in their 30s or younger. It decreased in all age groups. The use rate of beds is slightly less than 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 48 and 54, respectively, with a ratio of numbers for this week to last week of less than 1 (0.71 and 0.65). The use rates of beds are less than 10% in Tochigi and approximately 10% in Gunma.
In Tokyo, the number of new cases of infection is approximately 95, with a ratio of this week to last week of less than 1 (0.72). The infected individuals are mainly in their 30s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is slightly more than 10%, and the use rate of beds for severe cases is slightly less than 20%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 59, 54, and 70, respectively, with a ratio of this week to last week of less than 1 (0.63, 0.67, and 0.68). The use rates of beds are slightly more than 10% in Saitama, slightly less than 10% in Chiba and approximately 10% in Kanagawa.
In Aichi, the number of new cases of infection is approximately 106, with a ratio of this week to last week of less than 1 (0.72). The individuals are mainly in their 20s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is slightly more than 10%. In Gifu, Shizuoka and Mie, the ratio of this week to last week is less than 1 (0.80, 0.70, and 0.69, respectively), with the number of new cases of infection at approximately 132, 81, and 79. The use rates of beds are slightly less than 30% in Gifu, approximately 10% in Shizuoka, and slightly less than 20% in Mie.
In Osaka, the number of new cases of infection is approximately 114, with a ratio of this week to last week of less than 1 (0.71). The infected individuals are mainly in their 30s or younger. It decreased in all age groups. The use rate of beds and the use rate of beds for severe cases are both slightly more than 10%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection are approximately 81, 96, 93, 77, and 69, respectively, with a ratio of this week to last week of less than 1 (0.56, 0.58, 0.68, 0.72, and 0.69). The use rates of beds are slightly more than 10% in Shiga, Kyoto, Hyogo, and Wakayama, and less than 10% in Nara.
In Fukuoka, the number of new cases of infection is approximately 124, with a ratio of this week to last week of less than 1 (0.65). The individuals are mainly in their 20s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is slightly more than 10%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection are about 97, 152, 140, 110, 153, and 171, respectively, with a ratio to this week to last week of less than 1 (0.65, 0.91, 0.77, 0.65, 0.71, and 0.83). The use rates of beds are approximately 10% in Saga, slightly more than 10% in Nagasaki, slightly more than 20% in Kumamoto, slightly less than 20% in Oita and Miyazaki, and slightly less than 30% in Kagoshima.
The number of new cases of infection is the highest nationwide, at approximately 590, with a ratio of this week to last week of less than 1 (0.88). The infected individuals are mainly in their 30s or younger. It decreased in all age groups. The use rate of beds is slightly less than 40%, while the use rate of beds for severe cases is slightly more than 10%.
In Aomori, Iwate, Hiroshima, and Yamaguchi, the numbers of new cases of infection are approximately 105, 88, 122, and 103, respectively. The use rate of beds is about 20% in Aomori, Hiroshima, and Yamaguchi, and slightly more than 20% in Iwate.
The number of new infections reported continued to decrease in almost all regions nationwide. By region, the moving average for last week is lower than the peak of last summer in the Tokyo metropolitan area, Aichi, Osaka, Fukuoka and other metropolitan areas, as well as some regional cities. On the other hand, although the highest situation in Japan remains in Okinawa, it has been decreasing for about the last three weeks.
The number of new cases of infection by age group continued to decrease in all age groups, and a similar tendency has continued by region.
As the places of new cases of infection, the proportion of welfare facilities for the elderly, nursery schools, business establishments, and restaurants remains high. Recently, the proportion of schools, hospitals, and welfare facilities for people with disabilities is on the rise.
The number of new cases of infections showed an increasing trend after the end of Golden Week, but a decreasing trend continued thereafter. Regarding the future infection situation, short-term forecasts for metropolitan areas expect the decreasing trend to continue, but there is concern that the number of infected people will increase around the summer because (1) the immunity acquired by the third vaccination and infection will gradually decrease, (2) June is the rainy season, and the flow of people tends to be relatively restrained, but after July, due to the influence of summer vacation, an increase in contact is expected, and (3) there is a possibility that the Omicron variant will be replaced by a new strain, and it is therefore necessary to pay close attention to the impact on the medical care provision system.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
The nighttime population increases or decreases each week in some regions, while in other regions the number increases continuously. Since in some areas the number exceeds the peak at the end of last year, it is necessary to pay attention to the impact on the infection status.
The replacement by the BA.2 lineage has largely occurred and compared to the time when the BA.1 lineage was dominant, it may be a factor in a slowdown in the decrease. In addition, the BA.2.12.1 lineage and BA.5 lineage have been detected in Japan, and it is necessary to continue monitoring.
The third vaccination is proceeding, but it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the immunity acquired from previous infections is expected to gradually decline in the future.
When the temperature rises, it becomes easier to ventilate, due to climate conditions. However, when the temperature rises or the rainy season begins, rainfall may increase indoor activities.
In Okinawa, the number of inpatients, the use rate of beds, and the use rate of beds for severe cases continue to decrease. Nationwide also, with a continuing decreasing trend in the number of new cases, the use rate of beds is decreasing in almost all regions, and the number of patients in home care or who are adjusting medical treatment is decreasing in all regions.
In cases of difficult emergency transportation, despite regional differences in both suspected non-COVID-19 cases and suspected COVID-19 cases, the numbers are decreasing nationwide.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, or other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
The situation is lower than the peak last summer nationwide, but it is still high in more than half of the nation's regions, especially in regional cities. For this reason, it is necessary to thoroughly implement basic infection control measures and daily health management, and cooperate in efforts to reduce the risk of infection.
It is important for people to receive a third vaccination as soon as possible, regardless of type, once such vaccination becomes available. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health. It is also important to consider vaccination again for people who have not received the first or second vaccination.
Basic preventative measures are still effective against infection with the Omicron variant. Therefore, it is necessary to continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking. On the other hand, the use of a mask is not necessary outdoors, except when talking at a close distance. Especially in summer, removing the mask outdoors is recommended from the viewpoint of preventing heat stroke.
It is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. Although limited data suggest that the incidence of pneumonia is higher than that of seasonal influenza, this needs to be investigated through various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. Many of these people had resided at medical or elderly facilities before they were found to be infected. It has been reported that not a few persons have died from causes other than the novel coronavirus infection itself. In particular, some have refused highly invasive treatments, while others did not meet the definition of severe disease, due to a worsening of an underlying disease, or for other reasons. Attention should also be given to a possible increase in the number of infected individuals requiring hospitalization, as test-positive persons with an underlying disease may experience disease exacerbation due to infection, and elderly infected patients may develop other symptoms, such as heart failure and aspiration pneumonia, even in the absence of COVID-19 pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Overseas, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing worldwide. In Japan, the influx of the Omicron variant from overseas initially comprised both BA.1 and BA.1.1; however, BA.1.1 has since become dominant. Currently, it has been largely replaced by the BA.2 lineage. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. In comparing the severity of the BA.1 lineage and BA.2 lineage, some animal studies suggest that the BA.2 lineage may be more pathogenic, but it has also been reported that there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages.
The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. The XE lineage has been detected in quarantine. The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. The BA.4, BA.5, and BA.2.12.1 lineages have been detected in quarantine. Of these, the BA.5 and BA.2.12.1 lineages have also been detected in Japan. According to the US CDC, the BA.2.12.1 lineage reportedly has a 25% higher rate of increase in infected individuals than the BA.2 lineage. In some countries and regions, the detection rates of the BA.4, BA.5, and BA.2.12.1 lineages have increased, and the BA.2 lineage has been replaced by these variants, suggesting its superiority in terms of an increase in the number of infected patients. The National Institute of Infectious Diseases has suggested that although there are no reports indicating large differences in infectivity or severity, information on the overseas infection status and findings regarding the characteristics of the virus should be collected and analyzed, as before, and genomic surveillance should be continued for purposes of monitoring.
Figures (Number of new infections reported etc.) (PDF)
86th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (June 1, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is less than 1 (0.98, as of May 15), and the figure stands at 0.98 in both the Tokyo metropolitan and Kansai areas.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 196 (roughly 230 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.67).
The infected individuals are mainly in their 30s or younger. It decreased in all age groups. The use rate of beds is approximately 20%.
In Ibaraki, the number of new cases of infection is approximately 86, with a ratio of numbers for this week to last week of less than 1 (0.69). The infected individuals are mainly in their 30s or younger. The number has decreased slightly or decreased in all age groups. The use rate of beds is slightly more than 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 67 and 83, respectively, with a ratio of numbers for this week to last week of less than 1 (0.54 and 0.69). The use rates of beds are slightly less than 10% in Tochigi and slightly less than 20% in Gunma.
In Tokyo, the number of new cases of infection is approximately 131, with a ratio of this week to last week of less than 1 (0.76). The infected individuals are mainly in their 30s or younger. The number has decreased slightly or decreased in all age groups. The use rate of beds and the use rate of beds for severe cases are both slightly more than 10%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 94, 80, and 102, respectively, with a ratio of this week to last week of less than 1 (0.81, 0.76, and 0.76). The use rates of beds are slightly less than 20% in Saitama, approximately 10% in Chiba and slightly more than 10% in Kanagawa.
In Aichi, the number of new cases of infection is approximately 147, with a ratio of this week to last week of less than 1 (0.75). The individuals are mainly in their 20s or younger. The number has decreased slightly or decreased in all age groups. The use rate of beds is slightly less than 20%. In Gifu, Shizuoka and Mie, the ratio of this week to last week was less than 1 (0.83, 0.66, and 0.74, respectively), with the number of new cases of infection at approximately 164, 116 and 115. The use rates of beds are slightly more than 30% in Gifu, slightly more than 10% in Shizuoka, and approximately 20% in Mie.
In Osaka, the number of new cases of infection is approximately 161, with a ratio of this week to last week of less than 1 (0.74). The infected individuals are mainly in their 30s or younger. The number has decreased slightly or decreased in all age groups. The use rate of beds is approximately 20%, while the use rate of beds for severe patients is slightly more than 10%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection are approximately 145, 163, 136, 107, and 99, respectively, with a ratio of this week to last week of less than 1 (0.81, 0.72, 0.76, 0.78, and 0.60). The use rates of beds are slightly more than 10% in Shiga, Kyoto, and Hyogo, about 10% in Nara, and about 20% in Wakayama.
In Fukuoka, the number of new cases of infection is approximately 191, with a ratio of this week to last week of less than 1 (0.74). The individuals are mainly in their 20s or younger. It decreased in all age groups. The use rate of beds is approximately 20%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection are about 150, 168, 181, 168, 214, and 206, respectively, with a ratio to this week to last week of less than 1 (0.71, 0.78, 0.75, 0.76, 0.72, and 0.75). The use rates of beds are slightly more than 10% in Saga and Oita, slightly less than 20% in Nagasaki, slightly more than 30% in Kumamoto, slightly more than 20% in Miyazaki, and approximately 30% in Kagoshima.
The number of new cases of infection is the highest nationwide, at approximately 670, with a ratio of this week to last week of less than 1 (0.72). The infected individuals are mainly in their 30s or younger. It decreased in all age groups. The use rate of beds is slightly less than 50%, while the use rate of beds for severe cases is approximately 20%.
In Aomori, Iwate, Akita, Fukushima, Nagano, Hiroshima, Yamaguchi, and Kochi, the numbers of new cases of infection are approximately 124, 113, 83, 83, 98, 192, 135, and 142, respectively. The use rates of beds are slightly more than 20% in Aomori, Iwate, Fukushima, Nagano, and Hiroshima, and approximately 20% in Akita, Yamaguchi, and Kochi.
The number of new infections reported continued to decrease in most regions nationwide. By region, the moving average for last week is lower than the peak of last summer in the Tokyo metropolitan area, Aichi, Osaka, and other areas, while Okinawa remains the highest in Japan, although it has been decreasing for the last two weeks. In many regions, the epi curve of the day of onset does not show a rapid increasing trend.
The number of new cases of infection by age group is decreasing in all age groups, and the same tendency can be seen by region, but since an increasing trend can be seen in people in their 80s and older in some areas, it is necessary to continue to pay close attention to the infection status of the elderly.
As the places of new cases of infection, the proportion of schools, business establishments, and welfare facilities for the elderly remains high. In addition, the proportion of eating and drinking establishments has been on the rise in the last few days, especially among people in their 20s to 60s.
Regarding the future infection situation, the short-term forecast for metropolitan areas is for the decreasing trend to continue, but it is necessary to keep paying close attention.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection.
The nighttime population is continuously showing an increasing trend in more than half the regions in the country. In some regions, the number increases or decreases each week, while in other regions, the number increases continuously. Since in some areas the number increases as much as the peak at the end of last year, it is necessary to pay attention to the impact on the infection status.
The replacement by the BA.2 lineage has generally progressed, and compared to the time when the BA.1 lineage was dominant, it may be a factor in the increase in the number of newly infected individuals and the slowdown in the decrease.
The third vaccination is proceeding in the elderly as well as in younger people, but it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the retention of immunity due to previous infections may affect trends in occurrence, by region.
When the temperature rises, it becomes easier to ventilate, due to climate conditions. However, when the temperature rises or the rainy season begins, rainfall may increase indoor activities.
In Okinawa, the number of inpatients, the use rate of beds, and the use rate of beds for severe cases have largely leveled off. Nationwide, with a continuing decreasing trend in the number of new cases, the use rate of beds is decreasing in more than half the regions, and the number of patients in home care or who are adjusting medical treatment is decreasing in almost all regions.
Cases of difficult emergency transportation, both suspected non-COVID-19 cases and suspected COVID-19 cases, continue to decrease, but there are some regions where the number is increasing regardless of the increase or decrease in the number of infected people, showing regional differences.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Nationwide, the infection status continues to be higher than last summer's peak. For this reason, it is necessary to thoroughly implement basic infection control measures and daily health management and cooperate in efforts to reduce the risk of infection.
It is important for people to receive a third vaccination as soon as possible, regardless of type once such vaccination becomes available. People with the novel coronavirus disease may experience severe conditions even if they are young and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health.
Basic preventative measures are still effective against infection with the Omicron variant. Therefore, it is necessary to continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking. On the other hand, the use of a mask is not necessary outdoors, except when talking at a close distance. Especially in summer, removing the mask outdoors is recommended from the viewpoint of preventing heat stroke.
It is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. Although limited data suggest that the incidence of pneumonia is higher than that of seasonal influenza, this needs to be investigated through various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. Many of these people had resided at medical or elderly facilities before they were found to be infected. It has been reported that not a few persons have died from causes other than the novel coronavirus infection itself. In particular, some have refused highly invasive treatments, while others did not meet the definition of severe disease, due to a worsening of an underlying disease, or for other reasons. Attention should also be given to a possible increase in the number of infected individuals requiring hospitalization, as test-positive persons with an underlying disease may experience disease exacerbation due to infection, and elderly infected patients may develop other symptoms, such as heart failure and aspiration pneumonia, even in the absence of COVID-19 pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effect of a first vaccination against disease onset is markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Overseas, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing worldwide. In Japan, the influx of the Omicron variant from overseas initially comprised both BA.1 and BA.1.1; however, BA.1.1 has since become dominant. Currently, it has been largely replaced by the BA.2 lineage. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. In comparing the severity of the BA.1 lineage and BA.2 lineage, some animal studies suggest that the BA.2 lineage may be more pathogenic, but it has also been reported that there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages.
The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. Two cases of the XE lineage were identified in quarantine. The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. The BA.4, BA.5, and BA.2.12.1 lineages have been detected in quarantine. Of these, the BA.5 and BA.2.12.1 lineages have also been detected in Japan. According to the US CDC, the BA.2.12.1 lineage reportedly has a 25% higher rate of increase in infected individuals than the BA.2 lineage. In some countries and regions, the detection rates of the BA.4, BA.5, and BA.2.12.1 lineages have increased, and the BA.2 lineage has been replaced by these variants, suggesting its superiority in terms of an increase in the number of infected patients. The National Institute of Infectious Diseases has suggested that although there are no reports indicating large differences in infectivity or severity, information on the overseas infection status and findings regarding the characteristics of the virus should be collected and analyzed, as before, and genomic surveillance should be continued for purposes of monitoring.
Figures (Number of new infections reported etc.) (PDF)
85th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (May 25, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is above 1 (1.04 as of May 8), while the figure stands at 1.02 in the Tokyo metropolitan area and 1.06 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 291 (roughly 309 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.81). The individuals are mainly in their 20s or younger. The number is increasing only in those younger than 10, and is slightly decreasing or decreasing in other age groups. The use rate of beds is approximately 20%.
In Ibaraki, the number of new cases of infection is approximately 123, with a ratio of numbers for this week to last week of less than 1 (0.89). The individuals are mainly in their 20s or younger. It increased or slightly increased in those younger than 10 and those aged 70 or older, while it slightly decreased or decreased for other age groups. The use rate of beds is approximately 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 124 and 120, respectively, with a ratio of numbers for this week to last week of less than 1 (0.88 and 0.93). The use rates of beds are slightly more than 10% in Tochigi and slightly less than 20% in Gunma.
In Tokyo, the number of new cases of infection is approximately 172, with a ratio of this week to last week of less than 1 (0.92). The individuals are mainly in their 20s or younger. It increased or slightly increased in those younger than 10 and those aged 80 or older, while it slightly decreased or decreased for other age groups. The use rate of beds and the use rate of beds for severe cases are both slightly more than 10%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 116, 105, and 135, respectively, with a ratio of this week to last week of less than 1 (0.82, 0.90, and 0.91). The use rates of beds are slightly less than 20% in Saitama, approximately 10% in Chiba and slightly more than 10% in Kanagawa.
In Aichi, the number of new cases of infection is approximately 195, with a ratio of this week to last week of less than 1 (0.95). The individuals are mainly in their 20s or younger. It increases in patients younger than 10 and slightly increases in patients in their 30s and 60s. The number is slightly decreasing or decreasing in other age groups. The use rate of beds is slightly less than 20%. In Gifu, Shizuoka and Mie, the ratio of this week to last week was less than 1 (0.99, 0.93, and 0.98, respectively), with the number of new cases of infection at approximately 198, 176 and 157. The use rates of beds are slightly less than 30% in Gifu, slightly more than 10% in Shizuoka, and slightly more than 20% in Mie.
In Osaka, the number of new cases of infection is approximately 219, with a ratio of this week to last week of less than 1 (0.92). The individuals are mainly in their 20s or younger. The number is increasing only in those younger than 10, and is slightly decreasing or decreasing in other age groups. The use rate of beds is slightly more than 20%, while the use rate of beds for severe patients is slightly more than 10%. In Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection are approximately 228, 180, 136, and 166, respectively, with a ratio of this week to last week of less than 1 (0.99, 0.91, 0.83, and 0.85). In Shiga, the number of new cases of infection is approximately 179, with a ratio of this week to last week of more than 1 (1.02). The use rates of beds are slightly less than 20% in Shiga and Hyogo, slightly more than 10% in Kyoto and Nara, and slightly less the 30% in Wakayama.
In Fukuoka, the number of new cases of infection is approximately 259, with a ratio of this week to last week of less than 1 (0.95). The individuals are mainly in their 20s or younger. It increased or slightly increased in those younger than 10 and those aged 80 or older, while it slightly decreased or decreased for other age groups. The use rate of beds is slightly more than 20%. In Saga, Nagasaki, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection are approximately 209, 215, 223, 298, and 276, respectively, with a ratio of this week to last week of less than 1 (0.87, 0.97, 0.97, 0.88, and 0.96). In Kumamoto, the number of new cases of infection is approximately 243, with a ratio of this week to last week of more than 1 (1.03). The use rates of beds are slightly more than 10% in Saga, slightly more than 20% in Nagasaki and Miyazaki, approximately 30% in Kumamoto and Kagoshima, and approximately 20% in Oita.
The number of new cases of infection is the highest nationwide, at approximately 931, with a ratio of this week to last week of less than 1 (0.91). The infected individuals are mainly in their 30s or younger. It increased in those younger than 10 and those aged 70 or older, while it slightly decreased or decreased for other age groups. The use rate of beds is slightly less than 50%, while the use rate of beds for severe cases is slightly more than 20%.
In Aomori, Iwate, Akita, Yamagata, Fukushima, Ishikawa, Tottori, Hiroshima, Yamaguchi, Kagawa, and Kochi, the numbers of new cases of infection are approximately 180, 129, 106, 118, 151, 289, 132, 280, 159, 235, and 226, respectively. The use rates of beds are slightly more than 20% in Aomori, Akita, Ishikawa, Yamaguchi, and Kagawa, slightly less than 30% in Iwate, Fukushima, and Hiroshima, and about 20% in Yamagata, Tottori, and Kochi.
The number of new cases of infection did not continue to increase after the latter half of Golden Week, and it continues to decrease nationwide except for some regions. However, since there is a concern that the number of patients with infection may increase again from the epi curve on the date of onset, it is necessary to pay attention to future trends. By region, the moving average for last week is lower than the peak of last summer in the Tokyo metropolitan and other areas. In contrast, the moving average for last week is higher than the peak from the end of last year in Okinawa and Miyazaki. In particular, the number of new cases of infection in Okinawa continues to be the highest nationwide, although there is a decreasing trend. In other regions as well, it will be necessary to continue to pay attention to changes in the number of infected people.
The number of new cases of infection by age group continued to increase for persons younger than 10, but slightly decreased or decreased in other age groups. There is a marked increase in many regions, particularly in those under the age of 10, who continue to increase. Furthermore, in Okinawa, the increase in those under the age of 10 is particularly remarkable. The number aged 70 years or older also increases, and therefore it is necessary to continue watching the status of infection in the elderly.
Regarding the place of infection of newly infected people, the proportion in schools, nursery schools, kindergartens, etc. is high, while the proportion in restaurants is decreasing.
As for the future infection situation, it may be affected by factors that increase infections, such as the ongoing substantial replacement by the BA.2 lineage, as well as factors that suppress infection, such as a third vaccination, etc.
It is thought that infection status is affected by the following changes in factors that increase and suppress infection .
The nighttime population is showing an increasing trend in more than half the regions in the country. In some areas the number increases as much as the peak at the end of last year, and it is necessary to pay attention to the impact on the infection status.
The replacement by the BA.2 lineage has generally progressed, and compared to the time when the BA.1 lineage was dominant, it may be a factor in the increase in the number of newly infected individuals and the slowdown in the decrease.
The main purpose of a third vaccination is prevention of onset and aggravation. While the third vaccination is proceeding in the elderly and also in young people, it is expected that the vaccination rate will further improve as young people become targets of vaccination. However, it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the retention of immunity due to previous infections may affect trends in occurrence, by region.
When the temperature rises, it becomes easier to ventilate, due to climate conditions. However, when the temperature rises or the rainy season begins, rainfall may increase indoor activities.
In Okinawa, the number of inpatients and the use rate of beds are on a decreasing trend, but the use rate of beds for severe cases remains at the 20% level. Nationwide, with a continuing decreasing trend in the number of new cases, the use rate of beds is decreasing in nearly half the regions.
Cases of difficult emergency transportation, both suspected non-COVID-19 cases and suspected COVID-19 cases, tended to decrease, but there are some regions where the number is increasing regardless of the increase or decrease in the number of infected people, showing regional differences.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Nationwide, the situation is still higher than the peak last summer, and there is also concern about the possibility of rebound because the factors that increase and suppress infection will continue. For this reason, it is necessary for citizens and businesses to cooperate to maintain the decreasing trend in the number of infections, and to call for thorough basic measures against infection and daily health management, in order to prevent a resurgence in the number of new cases of infection.
It is important for people to receive a third vaccination as soon as possible, regardless of type, once such vaccination becomes available. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health.
Basic preventative measures are still effective against infection with the Omicron variant. Therefore, administrative officers, business operators, and citizens should continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible, because the Omicron variant is highly transmissible.
On the other hand, it is not always necessary to wear a mask as before if it is possible to secure sufficient distance from surrounding people outdoors, or even when it is not possible to get sufficient distance from the surrounding people outdoors if there is little (or almost no) conversation. However, it is still necessary to wear them outdoors in a crowd. After clarifying that not all preschoolers are required to wear masks, and that they shall not be forced to wear them, the information should be disseminated widely and thoroughly.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking.
In order to protect the lives of both ourselves and our families, and at the same time, to prevent the spread of infection with the Omicron variant, it is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. Although limited data suggest that the incidence of pneumonia is higher than that of seasonal influenza, this needs to be investigated through various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. Many of these people had resided at medical or elderly facilities before they were found to be infected. It has been reported that not a few persons have died from causes other than the novel coronavirus infection itself. In particular, some have refused highly invasive treatments, while others did not meet the definition of severe disease, due to a worsening of an underlying disease, or for other reasons. Attention should also be given to a possible increase in the number of infected individuals requiring hospitalization, as test-positive persons with an underlying disease may experience disease exacerbation due to infection, and elderly infected patients may develop other symptoms, such as heart failure and aspiration pneumonia, even in the absence of COVID-19 pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effect of a first vaccination against disease onset is markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Overseas, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing worldwide. In Japan, the influx of the Omicron variant from overseas initially comprised both BA.1 and BA.1.1; however, BA.1.1 has since become dominant. Currently, it has been largely replaced by the BA.2 lineage. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. In comparing the severity of the BA.1 lineage and BA.2 lineage, some animal studies suggest that the BA.2 lineage may be more pathogenic, but it has also been reported that there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages. In the UK, a small number of cases of reinfection with the BA.2 lineage after infection with the BA.1 lineage have been reported, and the affected patients were reported to have mainly been unvaccinated.
The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. Two cases of the XE lineage were identified in quarantine. The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. The BA.4, BA.5, and BA.2.12 1 lineages have been detected in quarantine. Of these, the BA.5 and BA.2.12.1 lineages have also been detected in Japan. In some countries and regions, the detection rates of the BA.4, BA.5, and BA.2.12.1 lineages have increased, and the BA.2 lineage has been replaced by these variants, suggesting its superiority in terms of an increase in the number of infected patients. The National Institute of Infectious Diseases has suggested that although there are no reports indicating large differences in infectivity or severity, information on the overseas infection status and findings regarding the characteristics of the virus should be collected and analyzed, as before, and genomic surveillance should be continued for purposes of monitoring.
Figures (Number of new infections reported etc.) (PDF)
84th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (May 19, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is below 1, at 0.97 (as of May 1). The figure stands at 0.94 in the Tokyo metropolitan area and 0.97 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 346 (approximately 402 in Sapporo City), with a ratio to the previous week of more than 1 (1.07). The individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; particularly, those in their 20s have increased markedly. The use rate of beds is approximately 20%.
In Ibaraki, the number of new cases of infection is approximately 134, with a ratio of this week to last week of more than 1 (1.08). The individuals are mainly in their 20s or younger. In particular, the increase among those in their 20s is marked. The use rate of beds is approximately 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 135 and 128, respectively, with a ratio of this week to last week of less than 1 (0.89 and 0.92). The use rates of beds are slightly more than 10% in Tochigi and approximately 20% in Gunma.
The number of new cases of infection in Tokyo is approximately 184, with a ratio of this week to last week of 1.0. The individuals are mainly in their 20s or younger. Numbers in all age groups are slightly increasing or increasing; particularly, those in their 20s have increased markedly. The use rate of beds and the use rate of beds for severe cases are both slightly more than 10%. In Chiba, the number of new cases of infection is approximately 112, with a ratio of this week to last week of 1.0. In Kanagawa, the number of new cases of infection is approximately 144, with a ratio of this week to last week of more than 1 (1.08). In Saitama, the number of new cases of infection is approximately 136, with a ratio of this week to last week of less than 1 (0.97). The use rates of beds are about 20% in Saitama, about 10% in Chiba and slightly less than 20% in Kanagawa.
In Aichi, the number of new cases of infection is approximately 206, with a ratio of this week to last week of more than 1 (1.13). The individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; particularly, those in their 10s and 20s have increased markedly. The use rate of beds is approximately 20%. In Gifu, Shizuoka and Mie, the ratios of this week to last week are more than 1 (1.09, 1.32, and 1.08, respectively), with the number of new cases of infection at approximately 200, 190, and 161. The use rates of beds are about 30% in Gifu, slightly more than 10% in Shizuoka, and slightly less than 20% in Mie.
In Osaka, the number of new cases of infection is approximately 236, with a ratio of this week to last week of more than 1 (1.06). The individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; particularly, those in their 20s or younger have increased markedly. The use rate of beds is approximately 20%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection are 181, 233, 194, 159, and 188, respectively, with a ratio of this week to last week of more than 1 (1.19, 1.13, 1.13, 1.22, and 1.06). The use rates of beds are slightly more than 10% in Shiga, Kyoto, and Nara, about 20% in Hyogo, and slightly less the 30% in Wakayama.
In Fukuoka, the number of new cases of infection is approximately 269, with a ratio of this week to last week of more than 1 (1.01). The individuals are mainly in their 20s or younger. Numbers in all age groups are slightly increasing or increasing; particularly, those in their 20s have increased markedly. The use rate of beds is approximately 20%. In Kumamoto and Miyazaki, the numbers of new cases of infection are approximately 238 and 325, respectively, with a ratio of this week to last week of more than 1 (1.11 and 1.13). In Saga, Nagasaki, Oita, and Kagoshima, the numbers of new cases of infection are approximately 230, 215, 226, and 288, respectively, with a ratio of this week to last week of less than 1 (0.80, 0.94, 0.99, and 0.97). The use rates of beds are slightly more than 20% in Saga, Nagasaki, Kumamoto, and Miyazaki, approximately 20% in Oita, and slightly more than 30% in Kagoshima.
The number of new cases of infection is the highest nationwide, at approximately 1014, with a ratio of this week to last week of more than 1 (1.13). The infected individuals are mainly in their 30s or younger. Numbers in all age groups are increasing; particularly, those in their 30s or younger have increased markedly. The use rate of beds is slightly more than 50%. The use rate of beds for severe cases is slightly more than 20%.
In Iwate, Akita, Fukushima, Ishikawa, Nagano, Okayama, Hiroshima, Yamaguchi, Kagawa, and Kochi, the numbers of new cases of infection are approximately 151, 140, 182, 300, 146, 252, 301, 164, 252, and 267, respectively. The use rates of beds are slightly more than 20% in Iwate, Akita, Ishikawa, Nagano, Okayama, Yamaguchi, Kagawa, and Kochi, slightly more than 30% in Fukushima, and about 30% in Hiroshima.
Regarding the number of new cases of infections, the moving average for last week has been on a decreasing trend in the past few days, except in some areas. However, it is still difficult to accurately evaluate the infection status due to the influence of Golden Week on the figures. By region, the moving average for last week is lower than the peak of last summer in the Tokyo metropolitan area. In contrast, the moving average for last week is higher than the peak from the end of last year in Okinawa and Miyazaki. In particular, the number of new cases of infection in Okinawa is the highest nationwide, and the highest ever, with the increasing trend still continuing. In other regions as well, it will be necessary to continue to pay attention to changes in the number of infected people.
The number of new cases of infection by age group slightly increased or increased in all age groups, particularly among those in their 20s nationwide, and there were also marked increases in many areas. In Okinawa, the number of new cases of infection continues to increase in all age groups. Particularly, the number of young people in their 30s or younger is markedly increasing, and the number of elderly people in their 60s or older is also greatly increasing. The infection status in the elderly must be carefully monitored in other regions.
The proportion of new cases of infection at schools has increased after the end of Golden Week. In addition, due to the emphasis on epidemiological surveys, a trend of increased infections in eating and drinking places is not always clear, but caution is required because the number of infected people in the younger generation is increasing.
As for the future infection situation, it may be affected by factors that increase infections, such as active movements of people during Golden Week and the ongoing substantial replacement by the BA.2 lineage, as well as factors that suppress infection, such as a third vaccination, etc. In addition, since the number of infected people in the younger generation continues to increase, continuous attention to future trends is necessary.
The infection status is affected by the following factors, which increase or suppress infection. However, it will be necessary to continue to pay close attention to the infection status, for some time in the future.
While there are areas where the nighttime population started to increase after Golden Week, mainly in metropolitan areas, there are also areas where the number increased sharply beyond the peak at the end of last year during Golden Week, but started to decrease afterward, and there are regional differences. In addition, it is necessary to pay attention to the influence on the future infection status due to active movement of people and an increase in opportunities for contact during Golden Week.
The replacement by the BA.2 lineage has generally progressed and compared to the time when the BA.1 lineage was dominant, it may be a factor in the increase in the number of newly infected individuals and the slowdown in the decrease.
The main purpose of a third vaccination is prevention of onset and aggravation. While the third vaccination is proceeding in the elderly and also in young people, it is expected that the vaccination rate will further improve as young people become targets of vaccination. However, it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the retention of immunity due to previous infections may affect trends in occurrence, by region.
As the temperature will rise day by day, it will become easier to ventilate, due to climate conditions. However, elevated temperatures and rainfall may increase indoor activities.
In Okinawa, the number of inpatients and the use rate of beds continue to increase, and the use rate of beds for severe cases remains at the 20% level. In other regions, the use rate of beds and the numbers of home care recipients and medical treatment adjustments have increased, with the exception of some areas.
As for cases of difficult emergency transportation, the national total is lower than the peak in the summer of last year, but there is a tendency for it to stop declining. The number is increasing in some regions regardless of the increase or decrease in the number of infected people, showing regional differences.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In particular, attention should be paid to the recent epidemic status in the East Asian region. For individuals who are found to be positive by an entrance test, a whole-genome analysis should continue to be performed, to monitor the strains that are spreading overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Although it is difficult to make an accurate assessment of the current infection status due to the influence of Golden Week, it is still higher nationwide than the peak last summer. For this reason, it is necessary for citizens and businesses to cooperate to maintain the decreasing trend in the number of infections, and to call for thorough basic measures against infection and daily health management, in order to prevent a resurgence in the number of new cases of infection.
It is important for people to receive a third vaccination as soon as possible, regardless of type, once such vaccination becomes available. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health.
Basic preventative measures are still effective against infection with the Omicron variant. Therefore, administrative officers, business operators, and citizens should continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible, because the Omicron variant is highly transmissible.
On the other hand, it is not always necessary to wear a mask as before if it is possible to secure sufficient distance from surrounding people outdoors, or even when it is not possible to get sufficient distance from the surrounding people outdoors if there is little (or almost no) conversation. However, it is still necessary to wear them outdoors in a crowd. After clarifying that not all preschoolers are required to wear masks, and that they shall not be forced to wear them, the information should be disseminated widely and thoroughly.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. In principle, eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking.
In order to protect the lives of both ourselves and our families, and at the same time, to prevent the spread of infection with the Omicron variant, it is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. Although limited data suggest that the incidence of pneumonia is higher than that of seasonal influenza, this needs to be investigated through various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. Many of these people had resided at medical or elderly facilities before they were found to be infected. It has been reported that not a few persons have died from causes other than the novel coronavirus infection itself. In particular, some have refused highly invasive treatments, while others did not meet the definition of severe disease, due to a worsening of an underlying disease, or for other reasons. Attention should also be given to a possible increase in the number of infected individuals requiring hospitalization, as test-positive persons with an underlying disease may experience disease exacerbation due to infection, and elderly infected patients may develop other symptoms, such as heart failure and aspiration pneumonia, even in the absence of COVID-19 pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effect of a first vaccination against disease onset is markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Overseas, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing worldwide. In Japan, the influx of the Omicron variant from overseas initially comprised both BA.1 and BA.1.1; however, BA.1.1 has since become dominant. Currently, it has been largely replaced by the BA.2 lineage. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. In comparing the severity of the BA.1 lineage and BA.2 lineage, some animal studies suggest that the BA.2 lineage may be more pathogenic, but it has also been reported that there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages. In the UK, a small number of cases of reinfection with the BA.2 lineage after infection with the BA.1 lineage have been reported, and the affected patients were reported to have mainly been unvaccinated.
The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. Two cases of the XE lineage were identified in quarantine. The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. In addition, one case of the BA.4 lineage and two cases of the BA.5 lineage were confirmed in quarantine. In some countries and regions, the detection rates of the BA.4, BA.5, and BA.2.12 1 lineages have increased, and the BA.2 lineage has been replaced by these variants, suggesting its superiority in terms of an increase in the number of infected patients. The National Institute of Infectious Diseases has suggested that although there are no reports indicating large differences in infectivity or severity, information on the overseas infection status and findings regarding the characteristics of the virus should be collected and analyzed, as before, and genomic surveillance should be continued for purposes of monitoring.
Figures (Number of new infections reported etc.) (PDF)
83th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (May 11, 2022). Material 1
Effective reproduction number: On a national basis, the most recent number is below 1, at 0.94 (as of April 24). The figure stands at 0.90 in the Tokyo metropolitan area and 0.94 in the Kansai area.
* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.
The number of new cases of infection is approximately 302 (roughly 313 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.92). The individuals are mainly in their 20s or younger. In particular, the increase among those in their 20s is marked. The use rate of beds is slightly less than 20%.
In Ibaraki, the number of new cases of infection is approximately 121, with a ratio of numbers for this week to last week of less than 1 (0.83). The individuals are mainly in their 20s or younger. In particular, the increase among those in their 20s is marked. The use rate of beds is slightly more than 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 134 and 132, respectively, with a ratio of numbers for this week to last week of less than 1 (0.83 and 0.94). The use rate of beds is slightly more than 10% in Tochigi and slightly less than 30% in Gunma.
In Tokyo, the number of new cases of infection is approximately 171, with a ratio of this week to last week of less than 1 (0.88). The infected individuals are mainly in their 30s or younger. The number has decreased slightly or decreased in all age groups. The use rate of beds and the use rate of beds for severe cases are both slightly more than 10%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 132, 105, and 127, respectively, with a ratio of this week to last week of less than 1 (0.85, 0.78, and 0.82, respectively). The use rates of beds are slightly more than 20% in Saitama, slightly more than 10% in Chiba, and slightly less than 20% in Kanagawa.
In Aichi, the number of new cases of infection is approximately 162, with a ratio of this week to last week of more than 1 (1.02). The individuals are mainly in their 20s or younger. The number is increasing in those in their 20s, and decreasing in other age groups. The use rate of beds is slightly more than 20%. In Gifu and Shizuoka, the numbers of new cases of infection are approximately 163 and 126, respectively, with a ratio of this week to last week of more than 1 (1.09 and 1.15, respectively). In Mie, the number of new cases of infection is approximately 136, with a ratio of this week to last week of less than 1 (0.98). The use rates of beds are slightly less than 20% in Gifu, and slightly more than 10% in Shizuoka and Mie.
In Osaka, the number of new cases of infection is approximately 198, with a ratio of this week to last week of more than 1 (1.03). The individuals are mainly in their 20s or younger. The number is increasing in those in their 20s, and decreasing in other age groups. The use rate of beds is slightly less than 20%. In Nara and Wakayama, the numbers of new cases of infection are 128 and 158, respectively, with a ratio of this week to last week of more than 1 (1.09 and 1.06). In Shiga, Kyoto, and Hyogo, the numbers of new cases of infection are 146, 188, and 158, respectively, with a ratio of this week to last week of less than 1 (0.99, 0.97, and 0.98). The use rates of beds are approximately 20% in Shiga and Hyogo, slightly less than 20% in Kyoto, slightly more than 10% in Nara, and slightly more than 20% in Wakayama.
In Fukuoka, the number of new cases of infection is approximately 251, with a ratio of this week to last week of less than 1 (0.96). The individuals are mainly in their 20s or younger. The number is increasing in those in their 20s and slightly increasing in those in their 60s, and decreasing slightly or decreasing in other age groups. The use rate of beds is approximately 20%. In Nagasaki, Kumamoto, and Oita, the numbers of new cases of infection are approximately 213, 191, and 212, respectively, with a ratio of this week to last week of less than 1 (0.90, 0.99, and 0.98). In Saga, the number of new cases of infection is approximately 263, with a ratio of this week to last week of 1.0. In Miyazaki and Kagoshima, the numbers of new cases of infection are approximately 250 and 281, respectively, with a ratio of this week to last week of more than 1 (1.05 and 1.01). The use rates of beds are slightly more than 20% in Saga, Nagasaki, and Kagoshima, approximately 20% in Kumamoto and Oita, and slightly less than 20% in Miyazaki. The use rate of beds for severe cases is approximately 20% in Miyazaki.
The number of new cases of infection is the highest nationwide, at approximately 797, with a ratio of this week to last week of more than 1 (1.19). The individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; however, those in their 10s to 20s have increased particularly markedly. The use rate of beds is slightly more than 40%. The use rate of beds for severe cases is slightly more than 20%.
In Aomori, Iwate, Akita, Fukushima, Ishikawa, Nagano, Hiroshima, Kagawa, and Kochi, the numbers of new cases of infection are approximately 174, 146, 175, 166, 228, 121, 232, 224, and 209, respectively. The use rates of beds are approximately 20% in Aomori, Kagawa, and Kochi, and slightly more than 20% in Iwate, Akita, Fukushima, Ishikawa, Nagano, and Hiroshima.
It should be noted that it is difficult to accurately evaluate the infection status at this point, because the number of examinations and tests was small during GW.
As for the number of new cases of infection nationwide, the number has continued to decrease in large cities, mainly in the Tokyo metropolitan area. On the other hand, in other regions, it has been increasing and decreasing repeatedly. Furthermore, in Okinawa, there is a difference in the time course of the infection status, as the number of cases continues to increase with a plateau period. By region, the moving average for the last week is lower than the peak of last summer in the Tokyo metropolitan area, etc. In contrast, the moving average for the last week is higher than the peak from the end of last year in Okinawa and Kagoshima.
Also, although it is not the moving average for one week, it is necessary to keep in mind that when comparing the nationwide infection status for the last 3 days (Sunday to Tuesday) with the same days of a week 2 weeks prior containing consecutive holidays, there is a tendency for an increase in infection. In addition, it is also necessary to assume that the number of reports will increase in the weeks following a period of consecutive holidays, due to the influence of increased opportunities for contact at travel destinations, as well as an increased probability of infection due to an increase in the nighttime population.
The number of new cases of infection by age group increased in persons in their 20s, but remained flat or decreased in other age groups. In the Tokyo metropolitan area, the number has remained flat or decreased in all age groups, while in several local cities such as Okinawa and Miyazaki, an increase among persons in their 20s has been observed. In Okinawa, the number of new cases of infection is increasing in all age groups. Especially, the number in teens has increased markedly, and the number in the elderly is continuing to increase.
As for the place of infection for new cases, the proportion of places that serve food and drink among those in their 20s is approximately 6%, showing an increasing trend (approximately 2% in all ages). It is necessary to pay attention to whether the increase in this age group will lead to a future spread of the infection, and also to give attention to the infection status in the elderly and effects on medical care.
As for the future infection situation, it may be affected by factors that increase infections, such as active movements of people during GW and the ongoing substantial replacement by the BA.2 lineage, as well as factors that suppress infection, such as a third vaccination, etc. Therefore, it is necessary to continue to monitor future trends.
The infection status is affected by the following factors, which increase or suppress infection. However, it will be necessary to continue to pay close attention to the infection status, for some time in the future.
While the nighttime population has decreased mainly in metropolitan areas, the number increased sharply after the peak time at the end of last year in some rural cities. In addition, it is necessary to pay attention to the influence on the future infection status due to active movement of people and an increase in opportunities for contact during GW.
The replacement by the BA.2 lineage has generally progressed, which may be a factor in the increase in the number of newly infected individuals and the slowdown in the decrease. Overseas, replacement by the BA.2 lineage is progressing, and the number of deaths has also increased with the spread of the infection in some countries (such as the UK). Accordingly, caution is required.
The main purpose of a third vaccination is prevention of onset and aggravation. While the third vaccination is proceeding in the elderly and also in young people, it is expected that the vaccination rate will further improve as young people become targets of vaccination. It should be noted that the protective effect against the Omicron variant is lower than that against the Delta variant, and the duration is short. The infection prevention effect of the third vaccination is expected to diminish over time. In addition, the retention of immunity due to previous infections may affect trends in occurrence, by region.
As the temperature will rise day by day, it will become easier to ventilate, due to climate conditions. However, elevated temperatures and rainfall may increase indoor activities.
In Okinawa, the number of inpatients, the use rate of beds, and the use rate of beds for severe cases have been increasing during GW. On the other hand, in other regions, the use rate of beds and the numbers of home care recipients and medical treatment adjustments have decreased, with the exception of some areas.
As for cases of difficult emergency transportation, the national total is lower than the peak in the summer of last year, but has shown a slight increasing trend after the decline stopped. There has been a slight increase in the number of suspected non-COVID-19 cases. In some regions, the number of suspected non-COVID-19 cases has been increasing with an increase in the number of infected patients, showing regional differences.
It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.
It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In particular, attention should be paid to the recent epidemic status in the East Asian region. For individuals who are found to be positive by an entrance test, a whole-genome analysis should continue to be performed, to monitor the strains that are spreading overseas.
In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.
Although the number of new cases of infection is decreasing nationwide, the current number of new infections continues to be higher than the peak last summer. Therefore, it is necessary for citizens and businesses to cooperate to maintain the decreasing trend in the number of infections, and to call for thorough basic measures against infection and daily health management, in order to prevent a resurgence in the number of new cases of infection.
It is important for people to receive a third vaccination as soon as possible, regardless of type, once such vaccination becomes available. People with the novel coronavirus disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health.
Basic preventative measures are still effective against infection with the Omicron variant. Therefore, administrative officers, business operators, and citizens should continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible, because the Omicron variant is highly transmissible.
Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. Activities with other persons should be carried out in a small group of people who usually meet each other. In principle, eating and drinking together should be done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking.
In order to protect the lives of both ourselves and our families, and at the same time, to prevent the spread of infection with the Omicron variant, it is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy. In particular, caution should be exercised when meeting persons who are at a high risk of severe illness, such as the elderly.
It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.
In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).
It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. Although limited data suggest that the incidence of pneumonia is higher than that of seasonal influenza, this needs to be investigated through various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. Many of these people had resided at medical or elderly facilities before they were found to be infected. It has been reported that not a few persons have died from causes other than the novel coronavirus infection itself. In particular, some have refused highly invasive treatments, while others did not meet the definition of severe disease, due to a worsening of an underlying disease, or for other reasons. Attention should also be given to a possible increase in the number of infected individuals requiring hospitalization, as test-positive persons with an underlying disease may experience disease exacerbation due to infection, and elderly infected patients may develop other symptoms, such as heart failure and aspiration pneumonia, even in the absence of COVID-19 pneumonia.
Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.
For infection with the Omicron variant, the preventive effect of a first vaccination against disease onset is markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.
Overseas, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing worldwide. In Japan, the influx of the Omicron variant from overseas initially comprised both BA.1 and BA.1.1; however, BA.1.1 has since become dominant. Currently, replacement with the BA.2 lineage is progressing. Therefore, this may affect the pace of the increase (decrease) in the number of cases of infection. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. In comparing the severity of the BA.1 lineage and BA.2 lineage, some animal studies suggest that the BA.2 lineage may be more pathogenic, but it has also been reported that there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages. In the UK, a small number of cases of reinfection with the BA.2 lineage after infection with the BA.1 lineage have been reported, and the affected patients were reported to have mainly been unvaccinated.
The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. Two cases of the XE lineage were identified from a sample collected in quarantine. The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. In some countries and regions, the detection rates of the BA.4, BA.5, and BA.2.12 1 lineages have increased, and the BA.2 lineage has been replaced by these variants, suggesting its superiority in terms of an increase in the number of infected patients. The National Institute of Infectious Diseases has suggested that although there are no reports indicating large differences in infectivity or severity, information on the overseas infection status and findings regarding the characteristics of the virus should be collected and analyzed, as before, and genomic surveillance should be continued for purposes of monitoring.
Figures (Number of new infections reported etc.) (PDF)