Assessing spread risk of Wuhan novel coronavirus within and beyond China, January-April 2020: a travel network-based modelling study

Shengjie Lai; Isaac Bogoch; Nick Ruktanonchai; Alexander Watts; Xin Lu; Weizhong Yang; Hongjie Yu; Kamran Khan; Andrew J Tatem

In terms of the initial importation risk of virus for each city during the two weeks before Wuhan's lockdown, nearly all other cities in Hubei Province were estimated to be high-risk areas (Figure 2a ). Other places with high risks were Beijing, Shanghai, Guangzhou and other large cities. In terms of the provincial level, the risks were high in Guangdong and Hunan, followed by Henan and Zhejiang (Figure 2b ). There was a significant correlation (r-squared = 0.59, p < 0.001) between the number of imported cases and the risk of importation estimated from traveller numbers from Wuhan within the two weeks before LNY's Day (Figure 3a ). Further, a high proportion of cases travelled with symptoms at the early stage of the outbreak, and the lag from illness onset to hospitalization decreased from a median of 6 days (Interquartile range: 4-7 days) in the first half of January 2020 to 3 days (1-5 days) in the second half ( Figure 4 ).