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There are two primary factors driving virus evolution - not killing the host and defeating the host's immune system. Killing the host, at least with humans, is

There are two primary factors driving virus evolution - not killing the host and defeating the host's immune system. Killing the host, at least with humans, is an evolutionary dead end, since we go out of our way to quarantine the body and destroy or permanently confine it. In humans, viruses typically evolve to be less severe and more infectious over time. There's significant evidence that omicron is less severe. At some point we should see an equilibrium reached with the coronaviruses, and the hope is that it'll be as mild as seasonal colds. Omicron could be a significant leap in that direction. https://apnews.com/article/coronavirus-pandemic-business-health-africa-south-africa-c8d09bed79be4a25f752237c0470961b https://apnews.com/article/coronavirus-pandemic-business-hea...

_whiteCaps_ 5y ago
> In humans, viruses typically evolve to be less severe and more infectious over time. There isn't consensus in the scientific community about that. Counterexamples: polio, rabies, avian flu in human hosts, Black Death. It isn't clear what category COVID19 will end up in.
somewhereoutth 5y ago
No human virus is known to have evolved to become more contagious and less virulent. Zero. None. Unfortunately this is just a (comforting!) myth. Feel free to provide an example virus if you think I'm wrong!
- robbedpeter 5y ago
  https://www.nature.com/articles/s41576-018-0055-5 https://www.nature.com/articles/s41576-018-0055-5 https://www.pnas.org/content/early/2014/11/26/1413339111?with-ds=yes https://www.pnas.org/content/early/2014/11/26/1413339111?wit... https://www.bbc.com/future/article/20200918-why-some-deadly-viruses-vanish-and-go-extinct https://www.bbc.com/future/article/20200918-why-some-deadly-... https://journals.asm.org/doi/full/10.1128/JVI.00694-10 https://journals.asm.org/doi/full/10.1128/JVI.00694-10 Covid related links have saturated any searches on viruses in general, and the doom&gloom "reporting"is at the top. There are a lot of papers and examples of what I'm talking about, though, it's just irritating to get at. Gain of function research gives us rapid and repeatable demonstrations of vital evolution. Viruses that don't kill their hosts and develop more and better mechanisms of infection or evasion of immune system defenses outcompete other variants. There are a lot of examples in animal viruses, but Sars and hiv are examples of recent relevance. To be clear, I'm not making the claim that this happens to all viruses - evolution doesn't work like that. A virus that leaves you mostly functional for a few months before it kills you is not at all an unlikely scenario. Viruses also exist concurrent with other variants, and they can mutate rapidly. There's no hard and fast rule, just influences and constraints that can manifest as trends. In my opinion, the ideal outcome for sars-cov2 at this point is that a super mild variant evolves that will confer robust natural immunity while spreading fast enough to prevent the spread of other variants. It could become more deadly - I hope it won't, and what we know of virus evolutionary pressures in humans hints that we could get lucky.
  - somewhereoutth 5y ago
    SARS and HiV are certainly not examples where a human virus has evolved to become more contagious but less deadly. SARS was not contagious enough to escape our control efforts, and HiV is mitigated by our anti viral drugs. Indeed it would be nice if a less severe strain out competed current COVID, but such a thing has never happened before (as far as we know) - and as you point out there is no selection pressure for mildness when death/disability occurs some weeks after the infection has been cleared.
    - robbedpeter 5y ago
      There are multiple strains of hiv. One of the papers I linked to is a detailed study investigating a less lethal, more infectious strain. Sars-cov1 also evolved a few strains that were more infectious and less lethal. Both effects, by the way, are usually associated with separate individual mutations. It's rare that a single change in DNA results in both effects.

_whiteCaps_ 5y ago

> In humans, viruses typically evolve to be less severe and more infectious over time. There isn't consensus in the scientific community about that. Counterexamples: polio, rabies, avian flu in human hosts, Black Death. It isn't clear what category COVID19 will end up in.

somewhereoutth 5y ago

No human virus is known to have evolved to become more contagious and less virulent. Zero. None. Unfortunately this is just a (comforting!) myth. Feel free to provide an example virus if you think I'm wrong!

robbedpeter 5y ago
https://www.nature.com/articles/s41576-018-0055-5 https://www.nature.com/articles/s41576-018-0055-5 https://www.pnas.org/content/early/2014/11/26/1413339111?with-ds=yes https://www.pnas.org/content/early/2014/11/26/1413339111?wit... https://www.bbc.com/future/article/20200918-why-some-deadly-viruses-vanish-and-go-extinct https://www.bbc.com/future/article/20200918-why-some-deadly-... https://journals.asm.org/doi/full/10.1128/JVI.00694-10 https://journals.asm.org/doi/full/10.1128/JVI.00694-10 Covid related links have saturated any searches on viruses in general, and the doom&gloom "reporting"is at the top. There are a lot of papers and examples of what I'm talking about, though, it's just irritating to get at. Gain of function research gives us rapid and repeatable demonstrations of vital evolution. Viruses that don't kill their hosts and develop more and better mechanisms of infection or evasion of immune system defenses outcompete other variants. There are a lot of examples in animal viruses, but Sars and hiv are examples of recent relevance. To be clear, I'm not making the claim that this happens to all viruses - evolution doesn't work like that. A virus that leaves you mostly functional for a few months before it kills you is not at all an unlikely scenario. Viruses also exist concurrent with other variants, and they can mutate rapidly. There's no hard and fast rule, just influences and constraints that can manifest as trends. In my opinion, the ideal outcome for sars-cov2 at this point is that a super mild variant evolves that will confer robust natural immunity while spreading fast enough to prevent the spread of other variants. It could become more deadly - I hope it won't, and what we know of virus evolutionary pressures in humans hints that we could get lucky.
- somewhereoutth 5y ago
  SARS and HiV are certainly not examples where a human virus has evolved to become more contagious but less deadly. SARS was not contagious enough to escape our control efforts, and HiV is mitigated by our anti viral drugs. Indeed it would be nice if a less severe strain out competed current COVID, but such a thing has never happened before (as far as we know) - and as you point out there is no selection pressure for mildness when death/disability occurs some weeks after the infection has been cleared.
  - robbedpeter 5y ago
    There are multiple strains of hiv. One of the papers I linked to is a detailed study investigating a less lethal, more infectious strain. Sars-cov1 also evolved a few strains that were more infectious and less lethal. Both effects, by the way, are usually associated with separate individual mutations. It's rare that a single change in DNA results in both effects.