Table 1 Phase classifications for the COVID-19 pandemic in this study
Phase | Infection situation |
|---|---|
Overseas pandemic phase Dec. 2019-Feb. 2, 2020 | The infection is spreading abroad from Wuhan, China. |
Early phase of domestic pandemic Feb. 3, 2020-Apr. 6, 2020 | This phase started when the Diamond Princess cruise ship arrived at Yokohama. Infections have occurred in some Japanese. It is possible to trace the history of contacts of all patients through epidemiological surveys. |
First domestic pandemic phase Apr. 7, 2020-May. 7, 2020 | A state of emergency is declared by the Japanese government. Infections have occurred in several prefectures; it is impossible to trace the history of contacts of patients through epidemiological surveys. |
First remission phase May. 25, 2020-Jul. 1, 2020 | The state of emergency is lifted by the government. The number of infected people declines and remains at low levels. |
Second domestic pandemic phase Jul. 2, 2020-Sep. 31, 2020 | Infections are spreading again, and the number of infected people is rising steeply, with the daily number of newly infected people in Tokyo > 100. |
Second remission phase Oct. 1, 2020-Nov.-Dec. 2021 | The number of newly infected people per day reaches a plateau. |