国立感染症研究所

33th meeting of the COVID-19 advisory board of Ministry of Health, Labour and Welfare (May 6, 2021).  Material 1

 

Evaluation of the latest infection status, etc.

Infection status

  • The number of new cases of infection nationwide is still in an increasing trend based on the reporting date despite a decreasing trend in the ratio of this week to last week, and the number in the most recent week is approximately 28 per 100,000 population. The numbers of severe patients and deaths are rapidly increasing. As infections spread through the elderly population, the numbers are likely to further increase hereafter.

    The effective reproduction number exceeded 1 in late February and has recently become 1.02 (as of April 19).

  • Since mid-April, the proportion of young patients in their 20s to 50s among severe cases has increased not only in Osaka but also in Tokyo. Moreover, the number of infected persons aged less than 20 years has increased in many regions.
  • Furthermore, it should be assumed that the number of examinations and tests reduced during the Golden Week holidays; when the number of cases of infection increases in a region, because of the movements of people during the holidays in addition to delayed examinations and reporting, the number of reports in the following week or later is added with cases which may have occurred during the holidays.
Analysis of infection status [local trends]

*The value of new cases of infections is the number of people per 100,000 in the total number for the latest week on the basis of reporting dates

  1. (1) Kansai area: Mainly in Osaka and Hyogo, the medical care provision systems and the public health systems are under very severe pressure. Emergency transportation has become more difficult in many cases, and it is still in such a critical situation that general medical care will be inevitably restricted. It has also become difficult to rapidly respond to worsened symptoms in patients recovering at home and receiving care at accommodation facilities. It is essential to reduce the number of new cases of infection to protect the system for necessary and timely care.
    In Osaka, Hyogo, Kyoto and Nara, the number of new cases of infection is high in all age groups, especially in their 20s and 30s. In Osaka, 1 month and a little more than 10 days have passed since the start of implementation of the priority measures, such as for prevention of the spread of disease, and the emergency measures, respectively. The ratio of this week to last week has hovered around 1. There is a movement of decrease in the latest value of new cases of infection, but it is still very high, about 79. Careful monitoring should be continued for the situation as there is concern about delayed reporting.
    In Osaka, the nighttime and daytime populations that had decreased since application of the priority measures further decreased considerably and rapidly after issuance of the Declaration of State of Emergency. They hit a record low, below the lowest level observed under the first Declaration of State of Emergency. The effective reproduction number is 0.94 in Osaka, Hyogo and Kyoto, and the number of new cases of infection is expected to decrease. However, there is concern about delayed diagnoses and reporting, and an estimation that the value may level off. Therefore, the changes in the number of cases of infection should be carefully monitored at least through mid-May.
    For the neighboring regions, there is a movement of decrease in the number of cases of infection in Hyogo, Nara and Wakayama. The positive rate remains at high levels, around 15%, in Hyogo. It has leveled off in Kyoto and Shiga. The number of new cases of infection in Hyogo, Nara and Kyoto was as high as about 54, 42 and 35, respectively.
  2. (2) Metropolitan area (Tokyo and 3 prefectures):
    In Tokyo, three weeks and a little more than 10 days have passed since the start of implementation of the priority measures, such as for prevention of the spread of disease, and the emergency measures, respectively. With the spread of infection in persons in their 20s to 50s, the number of cases of infection is still in an increasing trend as a whole, to about 40. The ratio of this week to last week is also in a decreasing trend, but has continued to be 1 or higher for nearly 2 months. The spread of infection has continued mainly in the central Tokyo and also in neighboring areas.
    After issuance of the Declaration of State of Emergency, both the nighttime and daytime populations considerably and rapidly decreased. They reached levels below the lowest ever observed under the second Declaration of State of Emergency. The population between 18:00 to 20:00 in particular considerably decreased owing to voluntary restraint on serving alcoholic beverages. The decrease continued in the latter half of the Golden Week holidays. However, the effective reproduction number is not less than 1, and the number of new cases of infection may continue to increase after the Golden Week holidays.
    In Tokyo, the number of persons receiving medical care at accommodations or at home, and cases in the process of arranging hospitalization also increased, and there is concern about an increase in the burden on medical care provision systems.
    In Saitama, Chiba and Kanagawa, two weeks have passed since the start of implementation of the priority measures, such as for prevention of the spread of disease. The number of new cases of infection has leveled off or slightly increased, i.e., about 20, 16, and 17, respectively. The nighttime and daytime populations started to decrease during the Golden Week holidays. The population at 18:00 or later is continuing to decrease in the latter half of the Golden Week holidays owing to voluntary restraint on serving alcoholic beverages. The effective reproduction number is around 1, and the number of new cases of infection may remain flat for a while.
  3. (3) Chukyo area: In Aichi, 2 weeks have passed since the start of implementation of the priority measures, such as for prevention of the spread of disease. The increasing trend in the number of new cases of infection is continuing across almost all generations, but primarily in persons in their 20s and 30s, with the value reaching about 29. In Nagoya City, the number increased in almost all age groups, mainly in 30s to 50s.
    After issuance of the Declaration of State of Emergency this time for Tokyo and the Kansai area to which the emergency measures are taken, the population during both nighttime and daytime rapidly decreased. The nighttime population has become very close to the lowest value recorded during the second Declaration of State of Emergency. However, the effective reproduction number has continued to be 1 or higher for the most recent week, and the number of new cases of infection may continue to increase after the Golden Week holidays.
    In Gifu and Mie, the number of new cases of infection remains high, i.e., about 22 and 17, respectively.
  4. (4) Other areas under priority measures, such as for prevention of the spread of disease (Miyagi, Okinawa, and Ehime): In Miyagi, the decreasing trend in the number of new cases of infection is continuing with a current value of about 9. The nighttime and daytime populations decreased after issuance of the Declaration of State of Emergency.
    In Okinawa, the decreasing trend in the number of new cases of infection is continuing from mid-April, but is still high, about 31. The numbers in persons in their 20s and 30s is in a decreasing trend, but the numbers in persons in their 70s or older increased. Increase in the number of inpatients is a concern as hospital beds are nearly completely occupied.
    In Ehime, the number of new cases of infection started to decrease to about 12.
  5. (5) Areas other than those listed above: In Fukuoka, the number of new cases of infection has rapidly increased, primarily in persons in their 20s and 30s, since mid-April and reached about 47. The number of severe cases also considerably increased. The positive rate during the Golden Week holidays is increasing and there is concern about the spread and continuation of the infection. The number of new cases of infection hit a record high last week, and the nighttime and daytime populations have decreased since around that time. However, the values have not reached the lowest level achieved during the period of the second Declaration of State of Emergency. The effective reproduction number is at a high level, 1.35. Rapid increase in the number of new cases of infection may continue. Bed occupancy rate is also rapidly increasing. It may lead to the spread of infection as in the Kansai area, and prompt actions are needed.
    In Oita, Saga and Nagasaki, movements of decrease, and then of re-increase were observed. Although there is a movement of decrease in Kumamoto, the cases of infection are increasing in Miyazaki, and a rapid increase was observed from late April in Kagoshima, indicating the spread of infection all over the Kyushu area.
    The number of new cases of infection has continued to increase in Hokkaido, mainly in Sapporo City, and reached a high level of about 28. The value is high, about 57 in Sapporo City. Severely ill patients in their 50s or younger, especially 40s, are increasing, and the number of inpatients exceeded that during the third wave. The use rate of beds exceeded 80% and there have been cases of wide-area medical transportation to outside the City. The effective reproduction number is at a high level, 1.41. The rapid increase in the number of new cases of infection is expected to continue after the Golden Week holidays.
    In other regions, the number of cases of infection has surged or continuously increased due to clusters, etc. The number of new cases of infection exceeded 15 in Fukushima, Gunma, Ishikawa, Okayama, Hiroshima, Tokushima and Kagawa. Particularly in Gunma, Okayama and Tokushima, the number of new cases of infection is high, i.e., about 25, 33, and 27, respectively (the ratio of this week to last week has been 1 or higher for 2 weeks or longer in Ishikawa, Okayama, Hiroshima and Kagawa.). Especially in Gunma, the effective reproduction number is high, 1.42, and there is concern that the rapid increase may continue.

Analysis of mutant strains

  • The proportion of mutant strains as variants of concern (VOC) remains high, exceeding 80%, in the Kansai area (Osaka, Kyoto, and Hyogo); such strains seem to have been replaced with existing ones. Replacement of the predominant variants is ongoing in other regions, e.g., about 60% in Tokyo and 70% in Aichi.
  • No age-specific trend of infection spread has been seen. The number of pediatric patients is not remarkably high.
  • There is a finding that the risk of disease becoming severer in persons in their 50s or younger for variants with N501Y mutation than with non-N501Y mutation. Further close investigation is required to prove it.
  • In any case, it is necessary to establish medical care systems and provide treatments assuming the possibility of increased risk of disease becoming severer due to variants with N501Y mutation.

Measures to be taken

  • A little more than 10 days have passed since issuance of the Declaration of State of Emergency. In the regions under the measures for the State of Emergency (Tokyo, Osaka, Kyoto and Hyogo), the nighttime population decreased and a movement towards decrease in the rate of this week to last week has been observed. However, the increasing trend in the number of cases of infection is continuing in Tokyo, and the number has leveled off or slightly increased in Saitama, Chiba and Kanagawa designated to be controlled under priority measures, such as for prevention of the spread of disease. In the Kansai area, the number of cases of infection has leveled off or appears to be decreasing. However, the medical care provision systems are still in critical conditions. Based on the situation that the priority measures, such as for prevention of the spread of disease, had only limited effects while the existing strains have been replaced with mutant strains (VOC), strong measures are required again for ordinary times after the end of the Golden Week holidays.
  • In the other areas under priority measures such as for prevention of the spread of disease, the number of cases of infection has continued to increase in Aichi, is in a decreasing trend but remains high, about 30 in Okinawa. Effective measures to inhibit the infection are required. In Miyagi, the decreasing trend in the number of cases of infection is continuing, peaking at early April, and the use rate of beds has also decreased. The decreasing trend has continued since late April also in Ehime. In these areas, measures to prevent recurrences are required.
  • The number of new cases of infection remains high in Fukuoka and Hokkaido, and the burden on the medical care provision system has already been heavy in regions where the cases of infection have rapidly increased/been continuously detected. Strong measures to inhibit the infection should be taken immediately.
  • Considering the effects of mutant strains (VOC), it is considered necessary to discuss the timings and details of such measures based on the effects of the measures having been taken so far in various regions including Osaka and Tokyo.
  • Clusters have diversified not only in restaurants but also in other scenes of infection including workplaces and settings of club/group activities. Cases of infection in workplaces are becoming prominent and social activities will resume after the Golden Week holidays. It is required to reinforce the measures to inhibit the infection, such as continuing to limit commuting after the Golden Week holidays by utilizing teleworking, etc.
  • The information on the importance of basic infection prevention, such as wearing a mask, should be delivered. It is also necessary to inform the differences in the characteristics of masks by materials, e.g., non-woven fabric. It is also necessary to inform that not only scenes with the “3Cs” (closed spaces, crowded places, and close contact settings) but scenes of two or one of them alone pose a risk of infection.
  • While the previously predominant strains have been replaced with mutant strains (VOC), it is necessary to take measures focusing on understanding of the actual situation using virus genomic surveillance in order to reinforce the measures against new mutant strains in line with local infection statuses and evaluations/analyses of epidemiological information.
  • In addition to the proven effect of vaccines to prevent onset of the disease, there have been research reports conducted after clinical use of vaccines in various countries, suggesting the effect to prevent aggravation or to prevent infection. Vaccination with such effects in wider populations can be expected to reduce severe cases and then inhibit the infection of the disease. Vaccination was initiated for the elderly, but it is necessary for the national and local governments to work together to offer vaccinations for many people as quickly and efficiently as possible.

Figures (Number of new infections reported etc.) (PDF)

Copyright 1998 National Institute of Infectious Diseases, Japan

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