COVID-19 in Japan: Insights from the Epidemiological Data Masahiro Sonoo 1 , Masashi Idogawa 2 , Takamichi Kanbayashi 1 , Takayoshi Shimohata 3 , Masahito Kobayashi 4 , Hideyuki Hayashi 5 1Department of Neurology, Teikyo University School of Medicine 2Department of Medical Genome Sciences, Research Institute for Frontier Medicine, Sapporo Medical University School of Medicine 3Department of Neurology, Gifu University Graduate School of Medicine 4Faculty of Economics, Yokohama National University 5Department of Chemistry, Faculty of Medicine, Osaka Medical College Keyword: COVID-19 , PCR検査 , 感染者死亡率 , 高齢化 , 弱毒化 , PCR , true infection rate , aging rate , attenuation of viral virulence pp.1023-1030
Published Date 2020/10/1
DOI https://doi.org/10.11477/mf.1416201643
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The coronavirus disease 2019 (COVID-19) pandemic is a worldwide peril. The PCR tests are widely used to detect infections. However, multiple regression analysis revealed no correlation between the examination rate among population (ER) and the success of containment, which is achieved by social distancing. ER and fatality rate were even positively correlated. Japan has been criticized for its very low ER, but it achieved better containment than other major countries with much higher ER on 29 May. The estimation of the true infection rate (TIR) among population revealed that the low fatality rate in Japan and other Asian countries is partly due to low TIR. Fatality of COVID-19 is highly accentuated in aged persons. Despite having the highest aging rate in the world, the fatality rate in Japan is relatively low. The corrected fatality rate of Japan is the second-lowest among the G20 countries. Mimicking the attenuation of viral virulence due to natural selection would be a promising strategy to overcome pandemic. The prevention of in-hospital transmission, especially from severe cases, would be the key to achieve this. Attenuation of the viral virulence in the second wave is evident in many European countries, and also in Tokyo.

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