nt is yct=∑s=114αwithin,syc,t−s+∑s=114αbetween,s∑r≠cdcr−1yr,t−s+∑s=114ρszt−s+xctβ+𝜖ct, where c is a city other than Wuhan, and yct is the number of new confirmed cases of COVID-19 in city c on date t. Regarding between-city transmissions, dcr is the log of the distance between cities c and r, and ∑r≠cdcr−