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1/ New paper! "Social distancing to slow the U.S. #Covid_19 epidemic", led by Mark Siedner ( @MGHMedicine @MonganInstitute @GlobalHealthMGH @mgh_id @AHRI_News) & @harlingg ( @UCLGlobalHealth & @AHRI_News), w/ Zahra Reynolds, Rebecca Gilbert, & @atheendar ( @PennMEHP @PennLDI)
2/ Social distancing is a mainstay of nonpharmaceutical public health intervention in epidemic settings. Most of you recognize this #FlattentheCurve figure from the @PNASNews paper by Richard Hatchett, Carter Mecher and Mark Lipsitch ( @mlipsitch): https://www.pnas.org/content/104/18/7582">https://www.pnas.org/content/1...
3/ For more about social distancing, see this thread (among many, many informative threads on #Covid_19) by @NAChristakis: https://twitter.com/NAChristakis/status/1234815825430949891?s=20">https://twitter.com/NAChrista...
4/ If you lift social distancing too early, then infections start coming back. Another figure you probably recognize is this @JAMA_current paper by @HowardMarkel et al.: https://jamanetwork.com/journals/jama/fullarticle/208354">https://jamanetwork.com/journals/...
5/ Given that @realDonaldTrump is itching to get the U.S. "opened up and just raring to go", we wanted to assess the extent to which social distancing has restrained the growth of the #Covid_19 epidemic. (We started shortly after this disastrous interview) https://www.politico.com/news/2020/03/24/trump-wants-to-restart-economy-by-mid-april-146398">https://www.politico.com/news/2020...
6/ Astoundingly-- Zahra Reynolds and Rebecca Gilbert collected the social distancing data in a few DAYS. That& #39;s a lot of trawling of state govt web sites. During March 10–27, all 50 states and the District of Columbia implemented at least one statewide social distancing measure.
7/ These measures included executive orders, state of emergency declarations, restrictions on travel, school closures, etc. Binding, statewide measures were included. Non-binding measures (eg, "recommendations") & lower-level jurisdiction actions (eg, county) were _not_ included.
8/ We merged our data on social distancing policies with the @NYTimes #Covid_19 data, which they helpfully posted on @github: https://github.com/nytimes/covid-19-data">https://github.com/nytimes/c...
9/ The first social distancing measures were implemented when the median size of the epidemic, across 50 states and D.C., was 36 cases (IQR, 17-72). The mean daily case growth rate at these times was 30.6%, corresponding to a doubling of total cases every 3.3 days.
10/ Here is our primary results slide: mean #Covid_19 daily case growth rate mapped against the date of the first statewide distancing measures:
11/ This figure shows that before implementation, mean daily case growth was relatively constant. Beginning 4 days after implementation (ie, accounting for incubation period), the growth rate declined by 0.8%/day. By day 14, doubling time had increased (from 3.3 days) to 5 days.
12/ Our estimate of the reduction in mean daily case growth corresponds to a reduction in total #Covid_19 cases from 26,356 to 23,266 at 7d after implementation of social distancing, and from 156,360 to 88,105 at 14d. (Obviously we can& #39;t be that precise)
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COMPOUND INTEREST
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COMPOUND INTEREST
13/ Fewer jurisdictions (n=30 as of Mar 30) have implemented restrictions on internal movement (ie, "lockdowns"). Generally these were enacted later, a median of 10d after the first social distancing measures (IQR 8-12), and at a median epidemic size of 415 cases (IQR, 147-1172)
14/ The mean daily case growth rate had _already_ been declining at this point. There was no additional decline in mean daily case growth after implementation of statewide restrictions on internal movement ("lockdowns"):
15/ We ********** do not ********** think that the take-home message of the previous figure is that "lockdowns don& #39;t work". It is very difficult to identify the independent effect of lockdowns. Probably some people who are smarter than us can figure that out.
16/ The effects we estimate are consistent with what can theoretically be expected to result from social distancing and other behavioral interventions-- such as described in this @medRxiv preprint by @thimui_pham and a team from @juliuscenter @UMCUtrecht: https://www.medrxiv.org/content/10.1101/2020.03.12.20034827v2">https://www.medrxiv.org/content/1...
17/ Our estimates are also consistent with what has historically been observed (cf. the Hatchett/Mecher/ @mlipsitch paper referenced at the beginning of this thread).
18/ LOTS of limitations: social distancing intensified as epidemic worsened, some counties initiated social distancing before state govts, states initiated lockdowns after other social distancing measures, SUTVA violations, incr& #39;d surveillance & testing, less "post" obs time...
19/ I& #39;ll conclude with a word from @NIAIDNews director Dr Anthony Fauci: "If you look at what& #39;s going on in this country, I just don’t understand why we& #39;re not doing that [ie., implementing a federally mandated stay at home order]" https://twitter.com/AC360/status/1245875533113671685?s=20">https://twitter.com/AC360/sta...
