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36th meeting of the COVID-19 advisory board of Ministry of Health, Labour and Welfare (May 26, 2021).  Material 1

 

Evaluation of the latest infection status, etc.

Infection status

  • The number of new cases of infection nationwide has decreased since mid-May on the basis of reporting dates, and the number in the most recent week is approximately 26 per 100,000 population. There may be a decreasing trend in the epi-curve on the basis of onset dates. While a levelling-off trend or a decreasing trend has been shown in some regions, other regions still face an increasing trend. The situation continues to require caution. The trend in the number of severe patients or deaths shifted from increasing to flat, but the latest level has remained high.
  • In particular, in the metropolitan areas such as the Tokyo, Kansai, and Aichi areas, the flow of people decreased by various measures, but as the predominant strains are being replaced by mutants first detected in the UK (B.1.1.7), it has taken longer than before until the number of new cases of infection decreases. Under such circumstances, the flow of people has recently increased in various regions. Attention should be paid to the situation including changes in the number of new cases of infection.

    The nationwide effective reproduction number stayed at around 1 and has recently become 0.95 (as of May 9), marking the drop below 1.

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. The effective reproduction number represents the mean value of the most recent week (as of May 10)

  1. (1) Kansai area
    • In Osaka, Hyogo, and Kyoto, 4 weeks have passed since the start of emergency measures. The number of new cases of infection is approximately 30, 22, and 24, respectively. In Osaka and Hyogo, the number of new cases of infection continues to decrease, and a decreasing trend has been also shown in Kyoto. The number in Osaka, however, is still at a high level above 25.
    • In Osaka, the nighttime and daytime populations keep at a level approximately 30% lower than the minimum value during the second declaration of the state of emergency. In Hyogo and Kyoto, the nighttime population remains at a level lower than the minimum value during the second declaration of the state of emergency. The effective reproduction number is 0.69, 0.64, and 0.85 in Osaka, Hyogo, and Kyoto, respectively. While the number of new cases of infection is expected to continue to decrease, careful monitoring is necessary including the de facto population after the improvement of the infection status.
    • Mainly in Osaka and Hyogo, the medical care provision systems and public health systems are under very severe pressure. In Osaka, the number of patients receiving care at accommodation facilities, the number of inpatients and the use rate of beds for severe patients are decreasing as is the number of patients receiving care at accommodation facilities in Hyogo, but the other numbers remain at the same level. Although the situation is expected to improve alongside the decrease in the number of new cases of infection, general medical care still remains restricted. Clusters in places such as elderly facilities continue to occur.
    • In Shiga, Nara, and Wakayama, the number of new cases of infection is on a downward trend to approximately 19, 18, and 8, respectively.
  2. (2) Metropolitan area (Tokyo and its 3 neighboring prefectures) 
    • In Tokyo, 4 weeks have passed since the start of emergency measures. In Saitama, Chiba and Kanagawa, 5 weeks have passed since the start of priority measures. The number of new cases of infection has been flat or declining since mid-May, to approximately 31, 16, 13 and 20, respectively. Many people are in their 20s to 50s. The ratio of this week to last week is recently below 1. On the other hand, there may be effects by fluctuations in the number of infected patients during the Golden Week holidays (GW). Considering this point, we cannot be over-optimistic about the future.
    • In Tokyo, the nighttime and daytime populations have been increasing to the lowest level during the second declaration of the state of emergency. In Saitama, Chiba, and Kanagawa, the trend has remained flat. If the flow of people continues to be on an upward trend in Tokyo, there is a possibility of a rebound, and therefore, caution is required.
  3. (3) Chukyo area
    • In Aichi, 2 weeks has passed since the start of emergency measures. The number of new cases of infection increased rapidly, but has been flat since mid-May, at a high level of approximately 48. Many people are in their 20s to 30s. The burden on medical institutions and public health centers has continuously increased, and the use rates of beds are at high levels. The medical care provision systems have been under severe pressure.
    • The nighttime population has slightly decreased and has fluctuated around the lowest level during the second declaration of the state of emergency. The daytime population has decreased since the declaration of the state of emergency. Five weeks or more have passed since the de facto population decreased, and it is necessary to carefully watch whether the number of new cases of infection decreases.
    • In Gifu and Mie, 2 weeks have passed since the start of priority measures. In Gifu, the number of new cases of infection has decreased since mid-May, to approximately 30. As the nighttime and daytime populations are decreasing, it is expected to decrease in the number of new cases of infection. In Mie, the number of new cases of infection has also decreased to approximately 12. In Shizuoka, the number of new cases of infection continued to increase, but has decreased after mid-May, to approximately 13. Attention should be paid to future trends.
  4. (4) Kyushu/Okinawa
    • In Okinawa, 6 weeks have passed since the start of priority measures. Emergency measures have been applied since May 23. In the metropolitan areas including Naha City and the Yaeyama area, the number of new cases of infection has surged mainly in the working generations in their 20s and 30s, and the number has remained at a high level of approximately 93. There have been infections in persons coming from outside the prefecture. The use rate of beds has increased and further burden may be imposed on the medical care provision systems due to increase in the number of infected patients. Although the percentage of patients in their 60s is low at present, there is particular concern that transmission of infection in the elderly could cause an increase of severe patients.
    • The nighttime population, which decreased after the priority measures, has increased during GW. As there was only a slight decrease after GW, the number of infected patients is expected to continue to increase in the future.
    • In Fukuoka, 2 week has passed since the start of emergency measures. The number of new cases of infection continued to surge mainly among people in their 20s to 30s, but has decreased since mid-May, to approximately 44. The ratio of this week to last week has recently been 1 or less. However, the number of infected patients remains at a very high level. The use rate of beds is also increasing, and there continues to be a heavy burden on the medical care provision systems.
    • The effective reproduction number is 1 or less, and it is expected that the number of new cases of infection will decrease. However, after emergency measures, there was only a slight decrease in the nighttime population, which has not decreased to the minimum level at the time of the second declaration of the state of emergency. Therefore, it is necessary to watch carefully.
    • In Kumamoto, 1 week has passed since the start of priority measures. The number of new cases of infection has decreased since mid-May, to approximately 26.
    • There is a downward trend in other prefectures in the Kyushu area, but the number of infected patients in Saga and Oita exceeds 15, reaching approximately 20 and 24, respectively. The ratio of this week to last week has been decreasing below 1 and may continue to decrease. However, it needs to be monitored continuously.
  5. (5) Hokkaido
    • In Hokkaido, 2 weeks and 1 week have passed since the start of priority measures and emergency measures, respectively. The number of new cases of infection is increasing to a high level of approximately 78. The number in Sapporo City is at a higher level of approximately 127. In addition, clusters have occurred at hospitals and welfare facilities. The nighttime and daytime populations have decreased since emergency measures. However, the ratio of this week to last week remains above 1, though there is a decreasing trend, and the increase may continue in future. The medical care provision systems in Sapporo have been under severe pressure and the use rate of beds remains at a high level. In addition, there have been cases of wide-area medical evacuations transported outside the city.
  6. (6) Other areas under emergency measures (Okayama and Hiroshima)
    • In Okayama and Hiroshima, 1 week has passed since the start of emergency measures. The number of new cases of infection has decreased in Okayama since mid-May and has started to decrease in Hiroshima as well, but it is still at a high level of approximately 35 and 43, respectively. The use rate of beds is at a high level in both prefectures. In both prefectures, the nighttime and daytime populations are continuously decreasing and the ratio of this week to last week has recently been 1 or less. It is necessary to carefully monitor whether the decreasing trend continues.
  7. (7) Other areas under priority measures, such as for prevention of the spread of disease (Gunma and Ishikawa)
    • In Gunma and Ishikawa, 1 week has passed since the start of priority measures. In both prefectures, the number of new cases of infection has been decreasing since mid-May, to approximately 17 and 27, respectively (in Ishikawa, the number has currently increased in clusters in school settings). The effective reproduction number was below 1 in both prefectures and the ratio of this week to last week has been below 1. The number is expected to decrease in the future, but attention should be paid to whether the trend continues.
  8. (8) Areas other than those listed above
    • The number of new cases of infection in Aomori, Toyama, Yamaguchi and Kochi exceeds 15, reaching approximately 16, 22, 21 and 20, respectively. There is a downward trend in Yamaguchi, and a levelling-off trend in Aomori, while an upward trend continues in Toyama and Kochi. It is necessary to pay close attention in future.

Analysis of mutant strains

  • The proportion of B.1.1.7 variants has become approximately 80% of the national total in screening tests, suggesting that the existing strains were almost all replaced by the mutant strains, except for some regions. As for B.1.617 (the mutant strain first detected in India) in Japan, there are cases where infection has been confirmed from people who have not traveled abroad.
  • It is necessary to establish medical care systems and provide treatments assuming the possibility of increased risk of disease becoming severer due to B.1.1.7.
  • In addition, it has been reported that B.1.617 is being replaced with the existing ones overseas, and it has been also suggested that this strain may be more infectious and transmissible than B.1.1.7. Therefore, it is necessary to continue analyses.

Measures to be taken

  • Although the downward trends may continue in the Tokyo metropolitan and Kansai areas, attention should be paid as there are fluctuations in the flow of people. In Aichi, it is necessary to keep a close watch on whether the number of infected patients will clearly decrease. The increase is expected to continue in Okinawa. The B.1.1.7 variants have almost replaced the existing ones nationwide. The variants are expected to be faster in expansion and it may take longer to curb the spread of the variants. In addition, the number of severe patients is increasing or remains at a high level in many regions, and therefore the increase of infected patients should be continuously reduced.
  • It takes longer than before until a decrease in the flow of people leads to a reduction in the number of new cases of infection. On the other hand, in some regions under emergency measures and those under priority measures, the number of infections has decreased or stopped increasing owing to cooperation of citizens and business operators, which indicates the effect of these measures. However, in regions where the number of infected patients continues to increase or has not decreased, the effect of these measures is still limited due to the influence of GW. In many regions, the number of new cases of infection has reached the level equivalent to the Stage IV, and the medical care provision systems continues to be under severe pressure. Therefore, continuation of necessary measures is required.
  • Based on the results of past efforts, the current infection status, the status of medical care provision systems, and the possibility that infection spread will progress faster than before due to B.1.1.7 and B.1.167, each local government needs to analyze the status of infection and the medical care provision systems at a conference body with experts in the regions and implement necessary measures in a timely manner.
  • It is essential to analyze and evaluate the timing of the priority measures and the emergency measures, their contents, and their effects during the expansion of the current epidemic, and to utilize the results for future operations. In addition, in each region, testing strategies utilizing the antigen qualitative tests and strengthening of the medical care provision systems should be carried forward based on the materials of the 33th ADB meeting and the discussions in the 5th Advisory Committee on the Basic Action Policy.
  • The effectiveness of vaccines has been reported. It is expected that vaccinations in wider populations can reduce severe cases and then inhibit infection of the virus. Vaccination in the large-scale vaccination centers has been initiated, and it is necessary for the national and local governments to work together to offer vaccinations for many people as quickly and efficiently as possible.
  • In some regions, the effects of masks are being analyzed. Taking into account these results, it is important to thoroughly wear a mask when conversing with others, including mealtimes. With the efforts in each region, it is indispensable to continue to communicate the importance of taking basic measures for infection control, such as proper wearing of masks, at various occasions in daily life, including workplaces and school settings. On the other hand, it is necessary ensure people understand that wearing a mask does not give complete immunity, and it should be also noted that compliance is difficult to ensure.
  • While it is estimated that the existing strains have been replaced with B.1.1.7 as the predominant strains in most regions with some exceptions, it is necessary to take measures focusing on understanding the actual situation using virus genomic surveillance in order to reinforce the measures against new mutant strains. Particularly for B.1.617, which has been positioned as VOC, it is essential to suppress the spread of infection in Japan as much as possible by following measures: nationwide monitoring through genomic surveillance, and active epidemiological surveys. In addition, while the border control measures have been strengthened, past measures need to be verified. Prompt actions will be required based on the occurrence status outside Japan and at quarantine stations in Japan, as well as the effects of the previous measures.

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

Copyright 1998 National Institute of Infectious Diseases, Japan