Fig. 1. Schematic illustration of geographic distribution, case composition, and clusters of all COVID19 cases in Xuzhou, China. (a) These cases were unevenly distributed in 10 ad-ministrative divisions. The top three divisions are Suining County (n=31), Pizhou City (n=15), and Jiawang District (n=7) while the bottom two divisions are Tongshan District (n=0) and Xinyi City (n=2). Red numbers in parenthesis indicate the number of imported cases. (b) Composition of imported and locally transmitted cases in terms of resident popu-lation in each administrative division. (c) 11 known clusters and the corresponding connec-tions among COVID19 cases in Xuzhou. All imported cases are in light green dots with an uppercase letter I. HB: Hubei province. Star symbol: Wuhan city. Note: It should be men-tioned that, although there were a total of 79 COVID-19 cases reported in Xuzhou during the pandemic, only 78 of them were included in the study for geographical epidemiological analysis because one COVID-19 patient was actually a train passenger and did not belong to any administrative division of Xuzhou City.Fig. 2. Interurban population migration from (a) Wuhan city or (b) Hubei province to other cities in China from the start of Spring Festival travel rush on January 10, 2010 to the lockdown of Wuhan on January 24, 2020. The number of confirmed cases is linearly related with the percentage of immigrant population from Wuhan city (R2=0.9332), but not from Hubei province (R2=0.4825).
