A variant rising in an area could be founder or stochastic effects (one version happened to catch in a superspreading event—this pathogen is very overdispersed) or actually outcompeting others through more transmissibility. That’s why it took time to establish B.1.1.7 was.
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Similarly, previous (not that well-established) claims of high infection rate through models based on (maybe, maybe-not accurate) nonrandom seroprevalance are NOT, by themselves proof of widespread reinfection, or even that reinfected cases are severe or equally contagious etc.
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I used to teach methods and stats for sociology students, and epidemiology examples were always very useful because they really are among the thorniest to try to untangle. And I believe harmful to overclaim, and not necessary to do so to make basic public health recommendations.
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zeynep tufekci Retweeted Eric Feigl-Ding
For example, the Brazil situation is horrific and deserves immediate attention, but this thread below is an example of how not to draw conclusions about P1 and it’s differential effect on young people. (The situation is bad enough without making unsupported claims like this).https://twitter.com/DrEricDing/status/1379995247812444162 …
zeynep tufekci added,
Eric Feigl-DingVerified account @DrEricDingLet this sink in—over **half of all intubated young adults** on ventilators now dies from#COVID19 in Brazil
. What’s odds last spring 2020? 1 in 3.
That is likely an effect of #P1 variant—not just ICU capacity because March 2021 wasn’t included yet.
(HT @terrence_mccoy) pic.twitter.com/mHY5Vfqu0iShow this thread12 replies 53 retweets 272 likesShow this thread -
Similarly, it’s likely that P1 is more transmissible than the wildtype, but what’s happening in Brazil is completely compatible with an unchecked epidemic causing hospital system collapse even without higher transmissibility let alone any—unproven, speculative—effect on severity.
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zeynep tufekci Retweeted Alexis C. Madrigal
Yes, of course. There are *SO MANY* confounders like that. We saw admission criteria change even in the United States during surges, affecting a lot of hospital-level statistics. Making claims about characteristics of variants/surges is hard, and it’s important to be careful.https://twitter.com/alexismadrigal/status/1380152737204072448 …
zeynep tufekci added,
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zeynep tufekci Retweeted Dr. Angela Rasmussen
Also. Do note that I’m not even coming close to claiming listing all possible issues/confounders in a thread, but just saying there’s a reason to be wary of back-of-the-envelope calculations that are either comforting (herd immunity!) or alarming (more severe among the young!).https://twitter.com/angie_rasmussen/status/1380149045365145600 …
zeynep tufekci added,
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zeynep tufekci Retweeted Zain Chagla
And more. These things really are hard, and there is no contradiction between epistemic humility when we do not yet understand all the characteristics of a surge/variant, and advocating to do all we can to limit the suffering regardless.https://twitter.com/zchagla/status/1380147897988177920 …
zeynep tufekci added,
Zain ChaglaVerified account @zchaglaReplying to @zeynepYes - especially in LMIC or places where testing is all over the place Young people coming in droves to ICU in an area with questionable testing could be a) Increased virulence b) Baseline risk with a LOT of younger people infected and only seeing tip of the iceberg.1 reply 9 retweets 124 likesShow this thread -
As a simple cautionary example on not being too confident about reinfections driving Brazil’s P1 surge, compare with Uruguay (no past surge, hence cannot be reinfections). Uruguay also has P1 at least rising. Maybe earlier blood-bank sero study is unrepresentative? Hard to know.pic.twitter.com/NMIDvIVKtr
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Replying to @zeynep
Yes, good point. Also Uruguay does an excellent job of testing in contrast to Brazil, with deaths and hospitalizations disproportionate to confirmed case numbers
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Exactly. Their epidemic response has been much better (hence managed to keep things under control earlier, too) so it is a good comparison case for the murky situation. Their numbers are also more reliable. But they are also now having a real surge/outbreak.
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