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

We estimate that infected individuals began arriving on a daily basis in other major population centres in early January in Scenario 1 (observed Chunyun travel profile and cordon sanitaire imposed) ( Figure 2B ). The estimated number of infected arrivals on a given day peaked on the day before the travel restrictions at 4 (95% uncertainty interval (UI) 1 -8) in Beijing, 10 (95% UI 5 -17) in Chongqing, 1 (95% UI 0 -4) in Hangzhou and 3 (95% UI 1 -7) in Shenzhen. Travel restrictions reduced the number of infected arrivals to below 1 in all four cities within two days ( Figure 2B ). In Scenario 2 (Chunyun travel profile without cordon sanitaire), the number of daily infected arrivals decreases slightly after the Chunyun travel period, then stabilizes ( Figure 2B ). In cities with populations below 7 million, infected individuals began arriving later, so the cordon sanitaire may have acted to delay or prevent the arrival of infected individuals ( Figure S1 ).