When can the lockdown end? The results in our new preprint in @WellcomeOpenRes illustrate how the eventual decorrelation between transmission and movement is likely a key feature of successful #COVID19 exit strategies. wellcomeopenresearch.org/articles/5-81/…
@SRileyIDD @DrCWalters @MRC_Outbreak
@SRileyIDD @DrCWalters @MRC_Outbreak
Using daily reported cases from mainland China and Hong Kong SAR, we estimated transmissibility over time and compared it to daily within-city movement, as a proxy for economic activity. 
Initially, movement and transmission were very strongly correlated. However, that correlation decreased rapidly after the initial fall in transmissibility. In general, at the end of the study period the correlation was no longer apparent despite substantial increases in movement.
At the very end of the study period, when China began to experience the re-introduction of a small number of cases from Europe and the United States, there is an apparent up-tick in transmission.
A similar analysis for Hong Kong shows that intermediate levels of local activity were maintained while avoiding a large outbreak. We observed no correlation between intra-Hong Kong movement and transmissibility.
Limitations: This work is an analysis of correlation, not causation. While within-city movement undoubtedly affects transmissibility, this analysis does not infer causation. We used confirmed case reports, which represent a proportion of the total number of infected individuals.
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