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> Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive b

> Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. Host death does not stop transmission of Covid-19 so I do not think this study is particularly relevant, if we’re reading it in that context.

jhgb 5y ago
But perhaps partial vaccination has a similar effect if you make transmission less likely and now only more transmissible mutations make the cut.
- noduerme 5y ago
  This is true, and I wonder whether partial vaccination didn't play a role in the rise of Delta. But more transmissible != more lethal.
  - jhgb 5y ago
    In the case of Delta it almost certainly didn't. But the fact that something happened through one mechanism doesn't mean that it can't happen through another mechanism.
- sweetdreamerit 5y ago
  Am I wrong if I think that the most transmissible mutations tend to win the competition towards the less contagious ones in any case?
__blockcipher__ 5y ago
> Host death does not stop transmission of Covid-19 Huh? It does for that host. Yeah their corpse can still spread it for awhile or whatever but they're no longer engaging in society.
- jdavis703 5y ago
  That depends. During the ebola outbreaks one of the vectors were funeral practices that involved coming in contact with the diseased corpse.
- perihelions 5y ago
  Parse it as "most covid patients don't die, so host death isn't a limiting factor in covid transmission".
  - __blockcipher__ 5y ago
    Ah, I see. I touched on this a bit in another comment but there's more factors than lethality at play. If a virus makes you sufficiently symptomatic you're much more likely to isolate. Conversely if it remains completely asymptomatic you will spread very little. So they're targeting a sweet spot of symptomaticity. You can very easily imagine a strain that would lead to the sweet spot of symptomaticity in a vaccinated person, which therefore would tend to "overshoot" and be excessively pathogenic in an equivalent unvaccinated individual. In fact, this is a bit of a tangent, but I suspect part of the reason the vaccinated are spreading Delta so much, is that it causes normal cold symptoms in them (which btw the original SARS-2 did too despite how people would act like it's way different); and imo because the media and the "expert" class has so sufficiently scared them that SARS-2 is this scary supervirus, they assume their run-of-the-mill cold symptoms can't be COVID and keep engaging in society without getting tested or anything * As very circumstantial evidence of the above hypothesis, I would point to https://www.nejm.org/doi/full/10.1056/NEJMc2009787 https://www.nejm.org/doi/full/10.1056/NEJMc2009787. This was before vaccination but it's a case report of people who actually had SARS-2 (if we can trust PCR; given the symptoms I think in this case they really did have it), and indeed had COVID (+ pre-existing risk factors) bad enough that they ended up developing strokes. And yet even though these were actual covid patients who eventually developed strokes: > "Social distancing, isolation, and reluctance to present to the hospital may contribute to poor outcomes. Two patients in our series delayed calling an ambulance because they were concerned about going to a hospital during the pandemic." So my interpretation of the above (this is me reading between the lines) is that even though they felt like shit, they thought actual COVID was even worse than that and thus avoided going to the hospital so they wouldn't catch COVID, not knowing that they already had it... * Note I don't necessarily think this (unintentional spread) is even a bad thing, I am firmly on the side of "SARS-CoV-2 will propagate through the population no matter what we do and the more we flail about and needlessly damage ourselves the worse it will be". But from the perspective of the average vaccinated person, they are probably very against the concept of spreading it and thus if they were aware that their "cold" was really SARS-2 they'd act way differently
perihelions 5y ago
I agree. To my understanding, it's basically the polar opposite -- it's primarily spread by walking, healthy-ish people in the early stages of disease. e.g. https://www.cidrap.umn.edu/news-perspective/2020/11/covid-19-most-contagious-first-5-days-illness-study-finds https://www.cidrap.umn.edu/news-perspective/2020/11/covid-19... ("COVID-19 most contagious in first 5 days of illness, study finds")

jhgb 5y ago

But perhaps partial vaccination has a similar effect if you make transmission less likely and now only more transmissible mutations make the cut.

noduerme 5y ago
This is true, and I wonder whether partial vaccination didn't play a role in the rise of Delta. But more transmissible != more lethal.
- jhgb 5y ago
  In the case of Delta it almost certainly didn't. But the fact that something happened through one mechanism doesn't mean that it can't happen through another mechanism.
sweetdreamerit 5y ago
Am I wrong if I think that the most transmissible mutations tend to win the competition towards the less contagious ones in any case?

__blockcipher__ 5y ago

> Host death does not stop transmission of Covid-19 Huh? It does for that host. Yeah their corpse can still spread it for awhile or whatever but they're no longer engaging in society.

jdavis703 5y ago
That depends. During the ebola outbreaks one of the vectors were funeral practices that involved coming in contact with the diseased corpse.
perihelions 5y ago
Parse it as "most covid patients don't die, so host death isn't a limiting factor in covid transmission".
- __blockcipher__ 5y ago
  Ah, I see. I touched on this a bit in another comment but there's more factors than lethality at play. If a virus makes you sufficiently symptomatic you're much more likely to isolate. Conversely if it remains completely asymptomatic you will spread very little. So they're targeting a sweet spot of symptomaticity. You can very easily imagine a strain that would lead to the sweet spot of symptomaticity in a vaccinated person, which therefore would tend to "overshoot" and be excessively pathogenic in an equivalent unvaccinated individual. In fact, this is a bit of a tangent, but I suspect part of the reason the vaccinated are spreading Delta so much, is that it causes normal cold symptoms in them (which btw the original SARS-2 did too despite how people would act like it's way different); and imo because the media and the "expert" class has so sufficiently scared them that SARS-2 is this scary supervirus, they assume their run-of-the-mill cold symptoms can't be COVID and keep engaging in society without getting tested or anything * As very circumstantial evidence of the above hypothesis, I would point to https://www.nejm.org/doi/full/10.1056/NEJMc2009787 https://www.nejm.org/doi/full/10.1056/NEJMc2009787. This was before vaccination but it's a case report of people who actually had SARS-2 (if we can trust PCR; given the symptoms I think in this case they really did have it), and indeed had COVID (+ pre-existing risk factors) bad enough that they ended up developing strokes. And yet even though these were actual covid patients who eventually developed strokes: > "Social distancing, isolation, and reluctance to present to the hospital may contribute to poor outcomes. Two patients in our series delayed calling an ambulance because they were concerned about going to a hospital during the pandemic." So my interpretation of the above (this is me reading between the lines) is that even though they felt like shit, they thought actual COVID was even worse than that and thus avoided going to the hospital so they wouldn't catch COVID, not knowing that they already had it... * Note I don't necessarily think this (unintentional spread) is even a bad thing, I am firmly on the side of "SARS-CoV-2 will propagate through the population no matter what we do and the more we flail about and needlessly damage ourselves the worse it will be". But from the perspective of the average vaccinated person, they are probably very against the concept of spreading it and thus if they were aware that their "cold" was really SARS-2 they'd act way differently

perihelions 5y ago

I agree. To my understanding, it's basically the polar opposite -- it's primarily spread by walking, healthy-ish people in the early stages of disease. e.g. https://www.cidrap.umn.edu/news-perspective/2020/11/covid-19-most-contagious-first-5-days-illness-study-finds https://www.cidrap.umn.edu/news-perspective/2020/11/covid-19... ("COVID-19 most contagious in first 5 days of illness, study finds")