What Roles Do Population and Migration Flows Play in the Spatial Diffusion of COVID-19 from Wuhan City to Provincial Regions in China?*

Population flow and migration flow are related but different. This research demonstrates the important roles of population and migration flows in the spatial diffusion of COVID-19 in mainland China using statistical analysis. Visitors are often considered responsible for the spread of COVID-19. Many migrants traveled back to their hometown from Wuhan city before 23 January 2020 for the spring holiday. They had stayed in Wuhan for a long time and had a higher risk to be infected than other short-term visitors. Thus previous migration flow is expected to have an indirect impact on the spatial diffusion of COVID-19 via population flow. It is found that the migration flows in 2005–2010 and 2010–2015 generally had larger correlation coefficients than real-time population flows based on big data on any day during 10–22 January 2020 with the number of COVID-19 cases. The average population flow in 8 days also had high correlation coefficients with the number of COVID-19 cases. The weighted average share of population flow and migration flow had the highest correlation coefficient with the number of COVID-19 cases on 26 January 2020. The COVID-19 risk for a migrant and a resident from an affected area could be 9 times that for a visitor.