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That’s only one pressure driving viral evolution. Another pressure is social response to infection: so far, the predominant response to a more-virulent or more

by zamfi 5y ago

That’s only one pressure driving viral evolution. Another pressure is social response to infection: so far, the predominant response to a more-virulent or more-lethal strain has been lockdown and/or other behavioral change, see: delta in India. On the flip side, a variant that causes milder symptoms is less likely to cause the same social response, which allows the virus to spread more widely. This may (may!) be what we’re observing with Omicron. In any case, we’ll know much more in a few weeks.

cableshaft 5y ago
I'd say that's normally true, but there's not a ton of lockdowns with even Delta right now, so while I agree that it probably isn't going to get worse, there's still not a ton of pressure from social response as it is right now for it to get milder (maybe you could argue pressure from vaccines I guess).
- daxfohl 5y ago
  Yeah I think we can learn what society thinks is acceptable risk just by looking at death counts over the last two years. They've pretty much leveled out. So as the virus mutates into less (or more) harmful variations, we'll see the world react less (or more) strictly, but overall death count will remain stable.
  - daxfohl 5y ago
    Presumably the steady state will happen after the virus mutates into a less dangerous variant (as infecting more people will be evolutionarily advantageous for the virus), and eventually we all get it and build up antibodies, at which point its virulence further subsides.
- zamfi 5y ago
  Sure, and this is where the immune erosion comes into play: as vaccination rates go up, so does selection pressure for immune erosion. Re: delta, think of this counterfactual — what would happen if a new variant appeared that is more lethal, more virulent, and that caused hospitalizations more quickly? You can bet the lockdowns would ratchet up. With Omicron, we didn’t even notice it until there was a random genome scan. Viral evolution rarely selects for host death — it’s just not useful as a goal. There’s also probably relatively weak selection pressure for symptoms, though probably casing sneezes in hosts helps with spread, it also acts as a signal that can cause the host to isolate and halt spread. (See: SARS v1.) From a selection pressure perspective, the ideal virus (among humans!) probably goes completely unnoticed for as long as possible. Humans won’t fight something they don’t even notice, and we probably have tons of these viruses everywhere and don’t even know about them.
mohanmcgeek 5y ago
Do you realise that mutation is not something the species can consciously control? How could the virus have mutated to become milder to suit the social response if the society, as it stands today, is continuing to do what they previously did..?
- RandallBrown 5y ago
  There's likely millions of virus variants out there already. Some will evolve to become much more contagious and most won't do much of anything. When a more severe variant starts dominating and everyone goes inside and stops spreading it that makes the more severe variant die out. As it dies out, and people go outside, variants that are milder will thrive because people won't lockdown as easily. This can repeat forever until eventually the virus is completely benign. Of course it's all based on randomness so it's not exactly predictable what will happen.
  - nostoc 5y ago
    Except "Everybody goes inside and stops spreading" is not something that is unique to a variant of concern. When everybody goes inside, all the variants stop spreading. The pressure is the same on every variants, so there's no source of evolutionary advantages on any variants.
    - skulk 5y ago
      > no source of evolutionary advantages on any variants. Any variant that is able to co-exist with (rather than kill) its host during a full lockdown has a significant advantage. We co-exist with several coronaviruses already.
      - zamfi 5y ago
        Only true if the virus lasts long enough to outlive a lockdown. So far that hasn’t been the case for the vast majority of single hosts.
    - zamfi 5y ago

by zamfi 5y ago

cableshaft 5y ago

I'd say that's normally true, but there's not a ton of lockdowns with even Delta right now, so while I agree that it probably isn't going to get worse, there's still not a ton of pressure from social response as it is right now for it to get milder (maybe you could argue pressure from vaccines I guess).

daxfohl 5y ago
Yeah I think we can learn what society thinks is acceptable risk just by looking at death counts over the last two years. They've pretty much leveled out. So as the virus mutates into less (or more) harmful variations, we'll see the world react less (or more) strictly, but overall death count will remain stable.
- daxfohl 5y ago
  Presumably the steady state will happen after the virus mutates into a less dangerous variant (as infecting more people will be evolutionarily advantageous for the virus), and eventually we all get it and build up antibodies, at which point its virulence further subsides.
zamfi 5y ago
Sure, and this is where the immune erosion comes into play: as vaccination rates go up, so does selection pressure for immune erosion. Re: delta, think of this counterfactual — what would happen if a new variant appeared that is more lethal, more virulent, and that caused hospitalizations more quickly? You can bet the lockdowns would ratchet up. With Omicron, we didn’t even notice it until there was a random genome scan. Viral evolution rarely selects for host death — it’s just not useful as a goal. There’s also probably relatively weak selection pressure for symptoms, though probably casing sneezes in hosts helps with spread, it also acts as a signal that can cause the host to isolate and halt spread. (See: SARS v1.) From a selection pressure perspective, the ideal virus (among humans!) probably goes completely unnoticed for as long as possible. Humans won’t fight something they don’t even notice, and we probably have tons of these viruses everywhere and don’t even know about them.

mohanmcgeek 5y ago

Do you realise that mutation is not something the species can consciously control? How could the virus have mutated to become milder to suit the social response if the society, as it stands today, is continuing to do what they previously did..?

RandallBrown 5y ago
There's likely millions of virus variants out there already. Some will evolve to become much more contagious and most won't do much of anything. When a more severe variant starts dominating and everyone goes inside and stops spreading it that makes the more severe variant die out. As it dies out, and people go outside, variants that are milder will thrive because people won't lockdown as easily. This can repeat forever until eventually the virus is completely benign. Of course it's all based on randomness so it's not exactly predictable what will happen.
- nostoc 5y ago
  Except "Everybody goes inside and stops spreading" is not something that is unique to a variant of concern. When everybody goes inside, all the variants stop spreading. The pressure is the same on every variants, so there's no source of evolutionary advantages on any variants.
  - skulk 5y ago
    > no source of evolutionary advantages on any variants. Any variant that is able to co-exist with (rather than kill) its host during a full lockdown has a significant advantage. We co-exist with several coronaviruses already.
    - zamfi 5y ago
      Only true if the virus lasts long enough to outlive a lockdown. So far that hasn’t been the case for the vast majority of single hosts.
  - zamfi 5y ago