Ascertainment rate of novel coronavirus disease (COVID-19) in Japan

Ryosuke Omori; Kenji Mizumoto; Hiroshi Nishiura

In addition to the proposed adjustment, it should be noted that the 6 ascertainment rate of severe cases needs to be additionally estimated, and such 7 estimation requires direct measurement of the total number of cases or infected 8 individuals by means of seroepidemiological study or other testing methods of all 9 samples (Nishiura et al., 2020) . That is, the actual total number of cases is greater 10 than what it was adjusted in the present study. Using seroepidemiological 11 datasets, we plan to address relevant issues in the future. Other limitations 12 include that (i) we did not explore detailed natural history, e.g. dynamically 13 changing symptoms over the course of infection, and underlying comorbidities, 14 (ii) we ignored right-censored data, e.g. the time delay from illness onset to 15 severe manifestations, for simplicity. The latter led us to underestimate the 16 ascertainment rate. (iii) it is worth noting that the data of age dependent severity 17 employed in our analysis is only based on the observed data in China. 18