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

These secondary cities may have a high risk of community-level transmission through the introduction of infected travellers from Wuhan, and then spread the virus to other tertiary cities by returning population movements after the LNY holiday, causing an even wider spread of the virus. As most of the cities in Hubei province have implemented the same travel controls as Wuhan before LNY, we defined the high-risk secondary cities outside of Hubei province as the cities within top 30 ranked cities (Supplementary Table S1 ) with the highest risk of importation from Wuhan defined above. Based on the 2015 Baidu dataset on population movement, the risk of spreading the virus from high-risk secondary cities to tertiary cities was preliminarily calculated as the averaged percentage of travellers received by each tertiary city out of the total volume of travellers leaving each high-risk secondary city during the four weeks following LNY's Day. We chose a period of four weeks because the returning flow of LNY's population movement, Chunyun, generally lasts four weeks.