The effect of inter-city travel restrictions on geographical spread of COVID-19: Evidence from Wuhan, China

Billy J Quilty; Charlie Diamond; Yang Liu; Hamish Gibbs; Timothy W Russell; Christopher I Jarvis; Kiesha Prem; Carl A B Pearson; Samuel J Clifford; Stefan Flasche; Petra Klepac; Rosalind M Eggo; Mark Jit

Where the sum of the daily estimated number of travellers ψt,leaving Wuhan for the dates tmin to tmax, divided by the sum of the daily outflow index from Wuhan σt, for the same date range, equals the scaling factor S. Combining evidence from the first three sources in Table S1 , we chose a scaling factor of 50,000. This assumes each unit of Baidu's migration index corresponds to 50,000 outbound travellers. This produced the most reasonable outbound travel volume estimates, using scaling factors of 120,003.40 and 138,412, found in Cao (2020) and Zhou (2020) respectively, yielded unrealistically large travel magnitudes. These scaling factors would suggest that on Beijing's . CC-BY 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.