Chinese cities that implemented a Level 1 response (any combination of control measures) preemptively, before discovering any COVID-19 cases, reported 33.3% fewer laboratory-confirmed cases during the first week of their outbreaks compared with cities that started control later
A separate analysis using regression models shows that, among specific control measures, cities that suspended intra-city public transport and/or closed entertainment venues and banned public gatherings, and did so sooner, had fewer cases during the first week of their outbreaks
The low level of peak incidence per capita, the early timing of the peak, & subsequent decline in daily case reports, suggest that transmission control measures weren't only associated with a delay in the growth of the epidemic, but also with a marked reduction in number of cases
The case reproduction number R0 was 3.15 prior to the lockdown in Wuhan - As control was scaled-up from Jan 23 onwards, the case reproduction number declined to 0.97, 2.01 and 3.05 (estimated as C1R0) in three groups of provinces, depending on the rate of implementation
Once the implementation of interventions was 95% complete everywhere (stage 2), the case reproduction number had fallen to 0.04 on average, far below the replacement rate (<< 1) and consistent with the rapid decline in incidence
Our model suggests that, without the Wuhan travel ban or the national emergency response, there would have been 744,000 (± 156,000) confirmed COVID-19 cases outside Wuhan by Feb 19, day 50 of the epidemic.
With the Wuhan travel ban alone, this number would have decreased to 202,000 (± 10,000) cases. With the national emergency response alone (without the Wuhan travel ban), the number of cases would have decreased to 199,000 (± 8500).
Thus, neither of these interventions would, on their own, have reversed the rise in incidence by Feb 19. But together and interactively, these control measures offer an explanation of why the rise in incidence was halted and reversed
But together and interactively, these control measures offer an explanation of why the rise in incidence was halted and reversed, limiting the number of confirmed cases reported to 29,839 -- 96% fewer than expected in the absence of interventions
control measures were strongly associated with the containment of COVID-19, potentially averting hundreds of thousands of cases by Feb 19, day 50 of the epidemic. Whether the means and the outcomes of control can be replicated outside China, are now under intense investigation
