In many ways, this should be entirely obvious, but we now have strong evidence that social distancing results in decreased #COVID19 transmission rates. 1/7

Modeling analyses can estimate changes in transmission over time based on case counts. Here we look at estimates of the "effective reproductive number" Re (the number of secondary infections caused by a primary infection) over time in different locations. 2/7

@flaxter and colleagues at @MRC_Outbreak estimate that Re went from ~3.5 to just greater than 1 in many European countries over the span of March as social distancing increased. https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/covid-19/report-13-europe-npi-impact/ 3/7

@seabbs and colleagues at @cmmid_lshtm have an amazing live dashboard that estimates changes in effective reproductive number through time. They estimate decreases across many European countries as well. 4/7 https://cmmid.github.io/topics/covid19/current-patterns-transmission/global-time-varying-transmission.html

@niket_h_thakkar and colleagues at @IDMOD_ORG estimate that Re decreased significantly in King County, Washington, from ~3.5 to just over 1 from late-Feb to mid-March. https://covid.idmod.org/#/ResearchandReports 5/7

Also as expected, but helpful to see, is a tight connection between people's mobility patterns (as estimated by aggregated data from Facebook in the @IDMOD_ORG example) and the transmission of the virus, again suggesting that social distancing works. 6/7

It is entirely decreases in Re through social distancing that have resulted in a slowdown in the rate of increase in daily case counts (figure from @jburnmurdoch). 7/7

Follow up: I should have said that exceeding testing capacity can be responsible for some of this slowdown in increasing case counts. This analysis looks at this: https://cmmid.github.io/topics/covid19/severity/global_cfr_estimates.html. Pretty flat for the US but evidence of decreasing detection in several other countries.