Sometime early last year, an arbitrary >15 minute limit was placed on classifying close contacts for tracing #Covid_19 transmission.
As @jmcrookston puts it, no one knows for sure why 15 minutes and believe me, if he is not sure, no one is. No one has looked harder. A
1/7
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Gradually over the year though, evidence started emerging that the virus does not wear a watch, i.e., 15 minutes is not a magical barrier. Busting the 15-minute myth further: 2/7
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https://www.cdc.gov/mmwr/volumes/69/wr/mm6943e1.htm … Outbreak in a prison. Correctional officer infected with ~17 minutes of cumulative exposure, not continuos, and he was wearing masks during all interactions 3/7
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Revised guidance from CDC. "Individual who has had close contact (within 6 feet for a total of 15 minutes or more)" Now 15 mins or more, cumulative, over 24 hours. https://www.cdc.gov/coronavirus/2019-ncov/php/public-health-recommendations.html … 4/7
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Two infections, from one person, seated over 4 meters away. One infection in ~5 minutes spent in same room 5/7 https://jkms.org/DOIx.php?id=10.3346/jkms.2020.35.e415 …
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Replying to @akm5376 @cohnkaren
I think the impact of
#SuperEmitters is underestimated. We know viral concentration in saliva and nose vary by 10^7. Simple math shows that the 90th and 99th percentiles are about 400x and 40000x more virulent. See calculations: https://github.com/chonghorizons/covid-estimators/wiki/SuperEmitters …1 reply 0 retweets 2 likes -
Replying to @ViralHelmets @cohnkaren
You may have already come across this great article by
@zeynep https://www.theatlantic.com/health/archive/2020/09/k-overlooked-variable-driving-pandemic/616548/ … regarding superspreaders and k value and dispersion of#COVID19 Its impact is known, not given due policy consideration yet, which is why, arbitrary limits of time and space are meaningless1 reply 0 retweets 3 likes -
Thanks! I had forgotten about that article. k in epidemiology is exactly right, but is hard to explain in 60 seconds to a busy school board.
#superemitters is easy to explain. 100 infected people. Do you want protection against just the middle case? Or against all 100? 10sec1 reply 0 retweets 2 likes -
Replying to @ViralHelmets @akm5376 and
@zeynep thanks for the great article on k from so long ago. Framing it as median case vs 99th percentile case also gives CDC cover. CDC guidelines protects most cases. But for the overdispersed#superemitters we now know more about (and b117 may exacerbate), need stronger rules2 replies 0 retweets 1 like
Thank you! Yes, the overdispersion is an opportunity (allows for better targeting and it also makes limiting introductions to places very important as we're not doomed with just a few introductions) but makes certain types of analyses/communication hard.
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I would believe it made
#scicomm harder if I had not read you. Now I believe others should just try harder1 reply 0 retweets 1 like -
@akm5376 I was thinking of writing up the SuperEmitter math issue and posting on Medrxiv. If I did a first draft, would you take a look? Aiming for a very short 1 page article (more like a note). DM me and we can discuss?@zeynep also, but I assume you're already super busy2 replies 0 retweets 2 likes - Show replies
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