Temporal relationship between outbound traffic from Wuhan and the 2019 coronavirus disease (COVID-19) incidence in China

Zaixing Shi; Ya Fang

Traffic volume is expressed as the Baidu Migration Index, a proprietary index derived based on cell phone positioning data and is proportional to the daily total number of people traveling out of Wuhan. Although the explicit relationship between the population size and the Baidu Migration Index is unclear, previous analysis has estimated that one unit of the index corresponds to approximately 44,520 travelers [4] . Using web scraping technique, we obtained the Baidu Migration Index data for outbound traffic from Wuhan to the 31 Chinese provinces from January 10 to February 29, 2020. We also extracted the percentage of people who traveled to each province from Baidu Migration Map. With these data, we estimated the volume of daily traffic from Wuhan to each province, calculated as Volume province,date = Total Volume date × Percentage province,date . Data for the same Lunar calendar period in 2019 were used as benchmark to make predictions for disease incidence if the travel ban had not been issued.