Estimating number of global importations of COVID-19 from Wuhan, risk of transmission outside mainland China and COVID-19 introduction index between countries outside mainland China

Haoyang Sun; Borame Lee Dickens; Mark Chen; Alex Richard Cook; Hannah Eleanor Clapham

This study quantifies, with uncertainty, the estimated number of cases imported from Wuhan to countries outside mainland China. As we use information from the places with the highest ratio of the reported case count to the volume of passengers from Wuhan, we are only estimating the number of importations if these places with the highest ratio are capturing all imported cases. Therefore our estimates should be viewed as a lower bound on the number of imported infections, given possible mild and asymptomatic infections. Even given this, we estimate that Indonesiawhich has reported 0 cases to date-would be expected to have more cases than this, in line with estimates from Lipsitch et al. 6 . In addition, in places that have identified some cases-such as Thailand, Japan, South Korea, Taiwan and Hong Kong, the US and Malaysia-we estimate that the imported number of cases from Wuhan is even higher than those reported. In some of these places, testing may be already increasing, but if not, our results would suggest that these places should be targets for increased screening and testing for SARS-CoV-2.