国立感染症研究所

39th meeting of the COVID-19 advisory board of Ministry of Health, Labour and Welfare (June 16, 2021).  Material 1

 

Evaluation of the latest infection status, etc.

Infection status

  • The number of new cases of infection nationwide has been declining with approximately 9 per 100,000 population for the latest week of reporting dates. There is a downward trend in regions where the infection has spread. However, there are regions where the decreasing speed has slowed due to an increase in the flow of people, and there is concern about a possible future rebound in these regions.
  • Along with the decrease in the number of new cases of infection, the numbers of severe patients and deaths have decreased.    

    The nationwide effective reproduction number has been declining and remains below 1 at 0.78 (as of May 30).

Analysis of infection status [local trends]

  *The value of new cases of infection is the total number for the latest week of reporting dates per 100,000 population.

  1. (1) Okinawa
    • The number of new cases of infection remains high at approximately 62, but continues to decrease. New cases are mainly in their 20s to 30s and the proportion of minors is also increasing. The use rate of beds remains high, and the hospitalization rate has been increasing as the number of patients receiving home care and those arranging hospitalization are decreasing in association with the decrease in the number of new cases of infection. Schools have been closed due to an increase in the number of infected patients aged 19 years and younger. The nighttime and daytime populations have decreased since the start of the emergency measures. Although the number of new cases of infection may decrease in the future, attention should be paid as to whether these trends will continue.
  2. (2) Hokkaido
    • The number of new cases of infection has continued to decrease to approximately 17. In Sapporo City, the center of infection spread, the number has decreased, but is still at a higher level of approximately 29. The number of new cases of infection is expected to decrease in the future, but the nighttime population, which had continued to decrease, has started to increase. Attention should be paid as to whether the downward trend in the number of new infections will continue. The use rate of beds has remained high in Sapporo City.
  3. (3) Kansai area
    • In Osaka, Hyogo, and Kyoto, the number of new cases of infection has been decreasing to approximately 9, 5, and 8, respectively. As the number of new cases of infection has been decreasing, there has been some improvement such as a decrease in the number of inpatients and severe patients, but clusters in facilities for the elderly are continuing. In Osaka, the nighttime and daytime populations are increasing, but remain at the level of the minimum value during the second declaration of a state of emergency. In Hyogo, the nighttime population remains at a level lower than the minimum value during the second declaration of a state of emergency. In Kyoto, there has been a slight decrease during the latest week. The number of new cases of infection is expected to decrease, but careful monitoring is necessary, also of the de facto population.
  4. (4) Metropolitan area (Tokyo and its 3 neighboring prefectures) 
    • In Tokyo, Saitama, Chiba, and Kanagawa, the number of new cases of infection has been decreasing to approximately 19, 8, 11, and 14, respectively. The ratio of this week to last week has been below approximately 1, but the level remains higher and the decreasing speed slower compared to the Kansai area. Particularly in Chiba and Kanagawa, it is almost flat. In Tokyo, both the nighttime and daytime populations have increased for 5 consecutive weeks. The numbers are returning to the level before the start of the declaration of a state of emergency. In Saitama, the number remains flat, but in Chiba and Kanagawa, both the nighttime and daytime populations have increased from the previous week. There is concern that it is becoming difficult to obtain cooperation with the measures. Particularly in Tokyo, if the upward trend will continue, there is strong concern about rebound and caution is therefore required.
  5. (5) Chukyo area
    • In Aichi, the number of new cases of infection has been decreasing to approximately 12. As the number of new cases of infection has decreased, the number of inpatients and severe patients has decreased, and the use rate of beds both for inpatients and for severe patients is decreasing. The nighttime population has increased slightly but remains at a low level. Although the number of new cases of infection may decrease in the future, attention should be paid as to whether these trends will continue.
    • In Gifu, the number of new cases of infection has been decreasing to approximately 7. The nighttime and daytime populations remain at a low level, and the number of new cases of infection is expected to decrease in the future. In Mie, the number has been decreasing to approximately 5. The nighttime population has been increasing, which leads to concern about possible rebound.
  6. (6) Other areas under emergency measures (Fukuoka, Okayama and Hiroshima)
    • In Fukuoka, the number of new cases of infection has been decreasing to approximately 6. As the number of new cases of infection has decreased, the numbers of inpatients and severe patients have also decreased, and the use rate of beds both for inpatients and for severe patients is decreasing. The nighttime population remains at a low level. The number of new cases of infection is expected to decrease in the future, but it is necessary to carefully watch whether these trends will continue.
    • In Okayama and Hiroshima, the number of new cases of infection has been decreasing to approximately 3 and 7, respectively. As the number of new cases of infection has decreased, the numbers of inpatients and severe patients have also decreased, and the use rate of beds both for inpatients and for severe patients is a on a downward trend. In Okayama, the hospitalization rate exceeds 50%. The nighttime population remains at a low level in both prefectures and the number of new cases of infection is expected to decrease in the future, but attention should be paid as to whether the downward trend in the number of new infections will continue.
  7. (7) Areas other than those listed above
    • In Yamanashi, the number of new cases of infection is approximately 17. The number increased due to the occurrence of clusters and then started to decrease, but it should be watched carefully.

Analysis of mutant strains

  • The proportion of variants of B.1.1.7 lineage (alpha variant) has become approximately 80% of the national total in screening tests, suggesting that the existing strains have almost completely been replaced by mutant strains, except for some regions. In addition, the number of reports of B.1.617.2 lineage variants (including delta variant) is increasing.
  • It has also been reported that the existing strains have being replaced by delta variants overseas, and that this strain may be more infectious and transmissible than alpha variants. It is therefore necessary to continue analysis.

Future outlook and measures to be taken

  • Although a downward trend in the number of new cases of infection may continue nationwide, attention should be paid to the increasing trend in the flow of people, since the existing strains were almost replaced by the variants of B.1.1.7 lineage (alpha variant) and the variants may be more infectious. There are some regions where the flow of people has already started to increase and there is a possibility that the number of new cases of infection may stop decreasing in these regions.
  • In regions under emergency measures and those under priority measures, such as for prevention of the spread of disease (priority measures), the number of infections has decreased owing to the cooperation of citizens and business operators, clearly showing the effect of these measures. In Okinawa and Hokkaido, however, the number of new cases of infection has remained at the level equivalent to the Stage IV. There are some regions where the medical care provision systems remain under severe pressure, although the burden has decreased alongside the decrease in the number of new cases of infection and patients who are receiving care. Therefore, it is necessary reduce the number of new cases of infection as much as possible to prevent a future rebound and to continue to control the increase even if the reduction stops. It is necessary to thoroughly implement the measures based on the "Measures to be taken after June during the declaration of the state of emergency" compiled by the government's Novel Coronavirus Response Headquarters on May 28.
  • Particularly in Tokyo, the flow of people continues to increase. If this trend continues, the number of infected patients will stop decreasing and rebound in future. Vaccinations have been performed mainly in the elderly, and therefore it is expected that severe cases may be suppressed in the elderly. However, if the number of infected patients continues to surge after a rebound, the number of severe patients may increase and the medical care provision systems will be overwhelmed. In addition, there is a burden associated with vaccination at medical institutions. Based on these points, efforts necessary to control the spread of infection should be continued in the future.
  • In other regions and regions where the priority measures are lifted, each local government has to analyze the flow of people, the status of infection and the medical care provision systems in a conference style with experts in the region, and implement the necessary measures in a timely manner, based on the possibility that infection will spread faster than before due to alpha variants and variants of B.1.617 lineage (including delta variants).
  • As for the spread of infection this time, the size, speed, and course of decrease differed among regions. These differences can be attributed to various factors including replacement by variants, contents and timing of the start/end of countermeasures, movement of people or gathering of persons who do not usually meet due to the turn of the start/end of fiscal year or Golden Week holidays, and the age group that became the center of infection, but further investigation is needed.
  • The number of vaccinations has already exceeded 19 million nationwide and approximately 14.5 million people have received the first vaccination. To suppress the spread of infection, it is necessary to promptly and smoothly carry out the vaccination of many people nationwide, including occupational vaccinations.
  • While it is estimated that the existing strains have been replaced by alpha variants as the predominant strain in most regions with some exceptions, it is necessary to take measures focused on an understanding of the actual situation using virus genomic surveillance in order to reinforce the measures against new mutant strains. It is particularly essential concerning mutants, including the delta variants, to suppress the spread of infection as much as possible by following the measures: nationwide monitoring through genomic surveillance and screening of L452R variants, strengthening of systems to conduct tests regionally and active epidemiological surveys. In addition, it is also necessary to continue to take the border control measures promptly.

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

Copyright 1998 National Institute of Infectious Diseases, Japan

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