Again: Viruses do not necessarily evolve to be milder—especially if they transmit early, like this one. Our immune system learning about it—via vaccines or infection—can mean better response next time, so milder experience. Not same as virus becoming intrinsically less virulent.https://twitter.com/zeynep/status/1465075561236250631 …
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Evolution is not a teleological process, bad match for a story-telling species' brain. Things seem to make sense—the just-so story—but we must go back to the mechanism. What's being selected for? How? FWIW, I don't think we have clarity on Omicron's intrinsic virulence, yet.
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No, this doesn't make sense. There is no intrinsic trade-off mechanism between the two, and situations where both can and do go up, like Delta. And the virus doesn't "care" if it eventually kills its host as long as it is spreading.https://twitter.com/PrinzMidas/status/1468228080024137737 …
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SARS-CoV-2 transmits early in the disease course, sometimes before symptoms, and severe illness and death comes much, much later, *after* the most infectious period. "Milder" to vaccinated or previously infected people is different than "it became intrinsically less virulent."
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Yeup. We know this in all sorts of areas. EG, in computer worms, as long as you don't kill the host too early your spread and your damage are disconnected.
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Isn’t selection also on replication within the host? Maybe even primarily, if these variants are being formed in single hosts.
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Seems that delta at least was formed this way. It’s great at replicating within a host. Transmissibility is a side-effect. As is virulence.
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The dose of the virus and the duration period of the exposure are the most critical determinants. High viral load within a short period of exposure time could produce clinical disease in any human host.
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SARS-CoV-2 does lots of nasty things, but the clotting responsible for death occurs *after* the virus has been lysed. Lysed viruses don't replicate—they're in pieces. As such, they're incapable of feedback encouraging attenuation as a function of transmission, or vice versa.
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Is there selection pressure towards ability to mutate faster? Crude comparison but I'm thinking re evolution of flowering plants or plants that reproduce sexually vs asexually. So here, could milder lead towards greater opportunities to mutate, and be fitter as a result?
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