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

We next probabilistically determine the risk of local transmission within countries outside mainland China. There is of course currently great uncertainty in these estimates, however some of the countries we estimate with the highest probability have indeed reported (limited) local transmission such as Thailand, the US, Singapore, Taiwan, Japan and the South Korea 18 . This information was not used to generate our estimates, but provides some validation for the model. In countries such as Singapore, intensive contact tracing of cases and testing of all pneumonia cases was implemented 19 , increasing the likelihood of finding community transmission. The impact of control measures after initial detected cases is not included in our model, but may alter the risk of onward transmission and should be considered in further iterations of the model as in other modelling work considering impact interventions under different transmission scenarios. 20, 21 Other countries that we estimate to be at high risk of local transmission, but that have not yet detected transmission 18 include Indonesia, Cambodia, Canada and the Philippines. For all these places, our results suggest there could be a consideration of expanding testing of pneumonia or influenza like illness cases beyond those who have currently travelled, to find community transmission as soon as possible after it occurs, as has been ongoing in Singapore 19 and has been recommended recently in some areas of the US 22 .