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Scientist @fredhutch, studying viruses, evolution and immunity. Collection of #COVID19 threads here: https://bedford.io/misc/twitter/

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Jun 8, 2020 9:46 PM
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The simple model I was using here is perhaps worth thinking about in terms of how to mitigate impact from protests or other potential sources of transmission. 1/7

Trevor Bedford (@trvrb):
I appreciate the feedback I’ve gotten on these estimates (and whether it’s even responsible to make them). A couple of things to emphasize here. 1/11 https://t.co/ZtEUtQOwTK
https://twitter.com/trvrb/status/1269783996109488130


Here, the idea is that new index cases (in blue) acquired at protests or otherwise will lead to successive rounds of downstream infections (in orange). Because the epidemic is in general barely controlled, we expect a cascade of infections from one infection in the community. 2/7

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  1. Total impact can be mitigated by seeking fewer index cases. A 50% reduction in index cases will reduce total onward infections by 50%. Reducing the number of index cases can be accomplished with masks, social distancing, etc… 3/7

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  1. Total impact can be mitigated by self-quarantine. If people attending protests had just 50% adherence to self-quarantine after attending a protest, then potential for onward transmission would be reduced by 50%. 4/7

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A known potential exposure event makes self-quarantine a good strategy for reducing onward spread. Household transmission is a risk; this study found mask wearing and hygiene within a household to strongly reduce secondary household transmission (https://gh.bmj.com/content/5/5/e002794). 5/7


  1. Finally, total impact can be mitigated by even small improvements in epidemic control. If #TestTraceIsolate can reduce community transmission by 10%, each index case leaves 50% fewer downstream infections. 6/7

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Importantly, these public health improvements would pay dividends across the board with all cases, not just cases that are acquired at protests. 7/7

Marc Lipsitch (@mlipsitch):
the nearly 1000 daily deaths now in the US would go down in a geometric series that had 16.7 instead of 20 times as many before it ended. This means sustained a ~1% reduction in transmission would save 3.3x1000=3300 deaths, or 3-15x the daily toll @trvrb gets for protests
https://twitter.com/mlipsitch/status/1269680205095940098

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