国立感染症研究所

31th meeting of the COVID-19 advisory board of Ministry of Health, Labour and Welfare (April 20, 2021).  Material 1

 

Evaluation of the latest infection status, etc.

Infection status

  • The number of new cases of infection nationwide has continued to increase since early March based on the reporting date, and the number in the most recent week is approximately 23 per 100,000 population. In addition to the Kansai Area, Tokyo Metropolitan Area, and Chukyo Area, the number of persons with infection is increasing in many local areas, and the rate of increase continues to be high. With the increase in the number of new cases of infection, the number of severe patients has rapidly increased from late March.

    The effective reproduction number exceeded 1 in late February and has recently reached 1.11 (as of April 3) The level remains below 1 in Miyagi, but above 1 in Tokyo and its 3 neighboring prefectures, Aichi, Osaka/Hyogo, and Okinawa as of April 4.

  • There is still an increasing trend in the number of persons infected with the mutant strain N501Y, designated as a variant of concern (VOC). The proportion of mutant strains (VOC) detected by screening test (mechanical calculation) has risen to approximately 80% in Osaka and Hyogo and approximately 30% in Tokyo, showing that the strains are rapidly replacing the existing strains. At present, there is no clear trend toward spread of infection in persons aged less than 15 years.
[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) Metropolitan area (Tokyo and its 3 neighboring prefectures): The number of new cases of infection has continued to increase since mid-March to approximately 30 in Tokyo. The cases in their 20s to 30s have increased markedly, and the ratio of this week to last week has remained 1 or higher beyond 1 month. The proportion of mutant strains (VOC) also increased. In Kanagawa and Saitama, the number of new cases of infection has continued to increase since April, and in Chiba, the figure has also started to increase since mid-April.
  2. (2) Kansai area/Chukyo area/Kyushu: The prevalent strains have been replaced with mutant ones in the Kansai area. Moreover, the number of cases of infection is increasing in all generations, especially in the those in their 20s and 30s. The number of cases of infection has rapidly increased since mid-March in Osaka and Hyogo, and the figure has also considerably increased since late March in Kyoto, Nara, and Wakayama. After that, the number has also surged in Shiga. In Osaka, the rate of increase has slowed, but the ratio of this week to last week was 1.31 and the number of new cases of infection was approximately 88, showing no decrease. In particular, in Osaka, Hyogo, and Nara, the medical care provision systems and the public health systems have been put under extremely severe pressure with the upsurge in numbers of new cases of infection.
    In Aichi, the number of new cases of infection has reached approximately 18, resulting from increase in almost all generations in their 60s or younger, mainly in persons in their 20s and 30s. The rate of increase also remains high. The number has also increased in Gifu and Mie.
    In Fukuoka, the figure has rapidly increased since mid-April reaching approximately 16, and there is also an increase in Saga and Nagasaki.
  3. (3) Areas other than those listed above: In Okinawa, the infection has rapidly spread since late March. The number of new cases of infection has leveled off since mid-April, but remains at a high level of approximately 54. While the proportion of persons with infection in their 20s to 50s is large, the number of inpatients has increased.
    In Miyagi and Yamagata, the figure started decreasing after the end of March, showing decrease in all generations in Miyagi.
    In other regions, the number of infections has surged, or has continuously increased due to clusters, etc. In Hokkaido, Aomori, Fukushima, Ibaraki, Gunma, Ishikawa, Fukui, Nagano, Gifu, Okayama, Tokushima and Ehime, the number of new cases of infection remains high exceeding 10, and in particular, in Tokushima and Ehime, the number is high at 31 and 18.

Analysis of infection status

  • In the Kansai area, the existing strains have been replaced by mutant strains and the spread of infection continues. The number of persons with infection continues to increase not only in Osaka and Hyogo but also in the neighboring local areas, and attention needs to be paid to a rapid increase in the number of cases of infection due to mutant strains (the proportion of severe patients in their 40s and 50s also has increased in Osaka). In Osaka, the infection route is unknown in more than 60% of cases, and infections in households, workplaces, and settings of club/group activities have been observed. In Osaka, 2 weeks after the start of the priority measures, such as for prevention of the spread of disease, nighttime population in downtown areas tends to be on a downward trend, and the increase rate has also decreased. However, the number of new cases of infection has continuously increased and it is expected that the number of persons with infection, number of inpatients, and number of severe patients will continue to increase in the future. The number of cases in which the coordination of emergency transportation is difficult has been increasing and medical care provision systems are already under extremely severe pressure. The necessary measures must be implemented more thoroughly and the necessary support should be provided.
  • In the Tokyo metropolitan area, the nighttime population rapidly increased in Tokyo after the Declaration of a State of Emergency was lifted. The number of cases of infection began to decrease thereafter, but the infection spread in those in their 20s and 50s, and the total cases of infection are increasing and the increase rate has also elevated. There is a spread mainly in the central Tokyo and also in neighboring areas. Infection continues to spread at restaurants, and infected cases in facilities, settings of club/group activities, and workplaces are observed. The proportion of mutant strains (VOC) detected by screening tests is also increasing, reaching approximately 30%. The decrease in the nighttime population in downtown areas was limited, which was seen only in hours from 8:00 p.m. to 10:00 p.m. The effects of the priority measures, such as for prevention of the spread of disease have not been clarified yet, and there are concerns about continuous spread of infection and rapid expansion. In addition, the number of persons receiving medical care at accommodations or at home, and cases in the process of arranging hospitalization has started to increase, and there is concern about an increase in burden on the medical care provision systems in the future. In Tokyo and its 3 neighboring prefectures, the priority measures, such as for prevention of the spread of disease became effective from today. There has been no clear trend toward a decrease in flow of people, and the number of persons with infection is estimated to increase for approximately 2 weeks hereafter.
  • In Aichi, the number of cases of infection has increased since late March mainly in people in their 20s and 30s, and the proportion of mutant strains (VOC) detected by a screening test also is above approximately 50%. In Nagoya City, the figure has increased in people in their 10s to 60s, and infection has been seen in facilities, settings of club/group activities, workplaces, and communities of foreigners. An increase in the number of persons with infection has been also seen in neighboring Mie and Gifu, and it is considered that a certain period will be required for taking effects of the priority measures, such as for prevention of the spread of disease, which became effective from today. There are concerns about continuous expansion of infection or rapid expansion.
  • In Fukuoka, the number of persons with infection mainly in their 20s to 30s has been rapidly increasing since mid-April and nighttime population is also increasing. In neighboring Saga and Nagasaki, there has also been an increase in the number of persons with infection, which brings on anxiety for continuous spread of infection and rapid expansion of infection.
  • In Miyagi, the number of new cases of infection has decreased in association with a decline in the flow of people in the night after 8:00 p.m. However, the flow of people up to 8:00 p.m. has been increasing, and attention should be paid to future trends.
  • The spread of infection is due to the increase in infected persons in their 20s and 30s in most areas. In some areas, the number of persons with infection increases in all generations. As infections spread through the elderly population, severe cases are likely to further increase hereafter.

Measures to be taken

  • In areas under the priority measures, such as for prevention of the spread of disease (Miyagi, Tokyo, Saitama, Chiba, Kanagawa, Aichi, Osaka, Kyoto, Hyogo, and Okinawa), actions to be taken for the application of the priority measures should be implemented steadily. Then, expansion of infection must be reduced during the Golden Week holidays, and infection should be suppressed by taking this opportunity. In particular, in areas where infection is expanding, it is necessary to adopt measures not only in restaurants at night but also in workplaces and settings of club/group activities. Further, concrete measures to reduce flow of people should be implemented.
  • In particular, in Osaka and Hyogo, the strains have already been replaced by mutant strains (VOC), resulting in a large number of persons with infection in all generations. The medical care provision systems have been under extremely severe pressure, and securing beds and healthcare professionals for patients in severe conditions, which are expected to increase, should be prioritized. Flexible support by the national government is also required. Together with ensuring efforts at restaurants, strengthened measures are required to further reduce contact with others.
  • In Tokyo, the number of persons with infection in their 20s to 50s has been increasing, and the effects of the priority measures, such as for prevention of the spread of disease, have not been clarified yet. There is a possibility of rapid expansion of infection as in the Kansai area in future, which causes concerns that this may overwhelm medical settings and have major effects on usual medical care. In addition, as the Tokyo metropolitan area has a significant impact on other areas through movement of people, strengthened measures to reduce contact with others and movement of people should be considered.
  • In other regions where the number of cases of infection is increasing, it is necessary to promptly make efforts to control the infection in view of the infection status. Based on such measures, it is required to secure medical care provision systems and public health systems to respond to further spread of infection, as well as to provide necessary support by the national government.
  • There is a nationwide trend of infection spread mainly in people in their 20s and 30s. Infection has been reported not only in restaurants but also in various settings such as workplaces and club/group activities. Infection control to reduce expansion in this generation is required and attention should be paid to the spread of infection to the elderly population. There has continuously been infection at daytime karaoke and restaurants. The communities of foreigners also needed attention. It is necessary to urge patients with symptoms to undergo the test followed by rapid conduct of the test. In addition, it is needed to communicate again the importance of basic infection prevention such as wearing a mask.
  • As the number of infected people increases, it is important to prevent infection among the personnel in medical and welfare facilities. Therefore, a system for prompt testing even in persons with mild symptoms should be organized, in addition to thorough implementation of preventive measures against infection and quick response to the occurrence of infection, as well as periodic testing for personnel.
  • The mutant strain N501Y (VOC) has been reported to have higher infectivity than the existing strain. Prompt action is required based on evaluations/analyses of epidemiological information on the regional status of infection, infectivity, and pathogenicity considering the recent increase in the number of cases of infection.

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

Copyright 1998 National Institute of Infectious Diseases, Japan

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