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

The second dataset is a more recent daily movement matrix at the city level based on data from Baidu's search app from January 1 st , 2015 to April 30 th , 2015. The last recorded locations of a user (or device) for each day were compared, and if the location changed, then we counted the user (or device) as someone who had moved from one city to another city. To understand the spread risk of 2019-nCoV from Wuhan into other cities via domestic population movement, we aggregated daily outflows of people from Wuhan to other cities across mainland China for the two weeks (the quarantine period of the virus) prior to the cordon sanitaire of Wuhan. As the travel ban took place on January 23 rd , 2020, just 2 days before LNY's day, and given that LNY's day in 2015 was February 19 th , we took February 17 th , 2015 as a reference of the lockdown day in our dataset. Using the second dataset, then the risk of importation for each destination city or province was preliminarily defined as the percentage of travellers received by each city or province out of the total volume of travellers leaving Wuhan during the two weeks before the city's lockdown.