Early evaluation of transmission control measures in response to the 2019 novel coronavirus outbreak in China

Background: An ongoing outbreak of a novel coronavirus disease (COVID-19) was first reported in December 2019 in Wuhan city, Hubei Province, and has spread throughout China and to other countries. On 23 January 2020, in an attempt to contain the epidemic, non-essential travel was prohibited in and out of Wuhan city, a major transport hub and conurbation of 11 million people. Since then China has implemented nationwide its highest level (Level 1) of emergency response to further contain the spread of infection within and among cities. Methods: We used generalized linear regression models to investigate the effect of the type and timing of transmission control measures on the spread of COVID-19 from Wuhan city, and on the growth of the epidemic in 296 other cities across China. In addition to the Wuhan city shutdown, as part of the emergency response, entertainment venues were closed, public gatherings banned, intra-city public transport (bus and subway rail) suspended, and travel to and from other cities prohibited. Findings: The Wuhan city travel ban slowed the dispersal of infection to other cities by an estimated 2.91 days (95% CI: 2.54-3.29) on average. Among the other urban centres across mainland China, cities that implemented control measures pre-emptively, before the first case was reported, had 37% fewer cases in the week following the first reported case (13.0, 95%CI 7.1-18.8) compared with cities starting control after the first case (20.6, 95%CI: 14.5-26.8). Among individual control measures investigated, the most effective were suspending intra-city public transport, and closing entertainment venues and banning public gatherings. Interpretation: The implementation of transmission control measures slowed the dispersal of infection from its origin in Wuhan city and reduced the numbers of cases reported during the early stages of the epidemic in hundreds of other Chinese cities.