Figure. Progression of coronavirus disease outbreak and changes in the case-fatality risk by crude and adjusted rates. Crude case-fatality risk is the cumulative number of deaths on a given day divided by the cumulative number of cases on the same day. We set the infectious period as 10 days (2); case-fatality risk as 3% (3); basic reproductive ratio (R0) as 2.5 (4); recovery rate as 1/13 day (5), that is, 13 days from illness onset to recovery; and the population size as 1 million. A) Changes in the number of subpopulations over time after the first infection. B) Changes in crude case-fatality risk after 13th day of exposure and aCFR calculated by using Wilson et al.’s method (1) and by using Mizumoto et al.’s method (6). aCFR, adjusted case-fatality risk.