Effect of evacuation of Japanese residents from Wuhan, China, on preventing transmission of novel coronavirus infection: A modelling study

Introduction: In late January 2020, the Japanese government carried out three evacuations by aircraft from Wuhan, China, to avoid further cases of coronavirus disease 2019 (COVID-19) among Wuhan's Japanese residents. Evacuation by aircraft may be an effective countermeasure against outbreaks of infectious diseases, but evidence of its effect is scarce. This study estimated how many COVID-19 cases were prevented among the Japanese residents of Wuhan by the evacuation countermeasure.

Methods: We constructed a SETAIR (susceptible-exposed-transitional-asymptomatic-infectious-recovered) model to capture the epidemic growth of COVID-19 cases in Wuhan to estimate the predicted number of COVID-19 cases among Wuhan's Japanese residents if evacuation had not occurred at the end of January. We used data on the number of COVID-19 cases confirmed in Hubei Province for the period Jan 20-Feb 16, 2020, and on the number of cases of Japanese residents who were evacuated by aircraft on Jan 29, 30, and 31.

Results: Eleven imported COVID-19 cases were reported on Feb 1 from among the total 566 evacuees who returned to Japan. In the case of no evacuations being made, the cumulative number of COVID-19 cases among Wuhan's Japanese residents was estimated to reach 25 (95% CI [20,29]) on Feb 8 and 34 (95% CI [28,40]) on Feb 15. A 1-week delay in the evacuation might be led to 14 additional cases and a 2-week delay to 23 additional cases.

Conclusions: Evacuation by aircraft can contribute substantially to reducing the number of infected cases in the initial stage of the outbreak.