Population Flow and Epidemic Spread: Direct Impact and Spatial Spillover Effect

Based on population migration data from Baidu and the spatial Durbin model, this paper examines the impact of population mobility on the spatial transmission of COVID-19 and provides a basis for forecasting epidemic transmission and guiding public health intervention plans from the perspectives of population mobility and geographical space. The results show that epidemic spreading displays a clear spatial pattern that includes not only spreading from Wuhan to the surrounding areas but also secondary transmission in the Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta regions through population flows. The epidemic degree in each area is directly affected by the number of population inflows from Wuhan and indirectly affected by the spatial spillover effect from other areas. Due to the lack of strict restrictions on population flows, the spatial spillover effect in areas outside Hubei gradually strengthened after the closure of Wuhan and exceeded the direct effect, and the intensity of population flows within Wuhan had a significant impact on the spread of the epidemic. Without considering the spatial spillover effect, the model will overestimate the impact of population inflows in Wuhan on the local epidemic and underestimate the total effect of regional patterns on epidemic transmission.