> we clearly have evidence that on a short timeframe a version with _wildly_ enhanced transmissibility has evolved. So speculating that changes will continue is reasonable.
So let's be clear: the claim is that the virus can mutate, therefore, any particular outcome is equally likely?
If I speculate that the virus will mutate into a hemorrhagic fever, like marburg or ebola, is that reasonable?
If I speculate that the virus will lose its pathogenicity, is that reasonable?
I'd find it helpful if you provided some thoughts on determining what's reasonable and what's not reasonable to expect from future variants. As I understand it, a virus dramatically changing its mode of transmission -- say going from respiratory to a hemorrhagic fever -- doesn't really happen. But we also have a decent understanding of how covid gets transmitted now, so have some way to anchor expectations. You're saying it's not reasonable for covid to evolve to become more likely to cause illness in children. If that's true that's great news, but I really have no way to evaluate such a claim. Why is that unreasonable? Wouldn't we need more insight into why children are currently less affected to speculate on how reasonable it would be for that to change?
I notice your profile you have a biology background. I don't, and am guessing most people here don't either, so I'd find it helpful to get an explanation of why you find a change that puts children at more risk unlikely (and I bet others would too).
> You're saying it's not reasonable for covid to evolve to become more likely to cause illness in children. If that's true that's great news, but I really have no way to evaluate such a claim. Why is that unreasonable? Wouldn't we need more insight into why children are currently less affected to speculate on how reasonable it would be for that to change?
The short answer is that evolution is random. It isn't an intentional process. The virus isn't trying to become more infectious, or deadlier, or...anything, really. It's just a random process, filtered by some outside force(s). And in this case, the relevant outside forces acting on the virus are: 1) the human immune system's ability to see the virus, and 2) the virus' ability to bind to our cells.
If you're vaccinated (but not previously infected), your immune system can basically only efficiently recognize a bunch of little chunks of the spike protein of the virus -- the piece that allows the virus to bind to your cells. So any random mutations to that spike protein are potentially beneficial, in that they can maybe hide the virus from your immune system, or maybe increase how tightly the virus binds to your cells, or they can be potentially detrimental, in that they can maybe cause the virus to bind less tightly to your cells, or make the spike protein misshaped or something. Or they can do nothing at all.
These are essentially the only "forces" related to vaccines that are guiding the evolutionary process: forces that attempt to change the structure of the spike protein to either escape the immune system, increase cellular affinity, or decrease cellular affinity. The vaccines do nothing to influence anything else. All other dimensions are random, with respect to the vaccine.
Viruses are pretty stupid. If you want to imagine that the virus could become "more fatal" (somehow; it's not clear how this would happen), it has to be done within this framework. There was to be some process that is selecting for the viruses that are "more fatal", and that process needs to be somehow more efficient when only a fraction of the human population recognizes the little bits of the spike protein encoded by the vaccines.
Can this happen? Sure, anything is possible. Is it plausible? No, not really.
> the claim is that the virus can mutate, therefore, any particular outcome is equally likely?
No.
Did you actually read the study I linked?
Outcomes that enhance transmissibility are always being selected for. Things like higher viral load in the vaccinated.
That which spreads, spreads.
All things being equal, pathogenicity is neutral and gets down-selected when the pathogenicity conflicts with the ability to spread. But with two different populations, the feedback loop that of down-selective pressure against spread limitations due to pathogenicity may be broken.
If it spreads in one population which requires characteristics that make it lethal in the other population.
Yes. It makes the general argument (not specific to Covid) that is known to any evolutionary biologist: partial selective pressure causes an organism to evolve away from that pressure. It's why we tell people to take their entire course of antibiotics.
It in no way implies that the organism will evolve to do anything else. You wrote this:
> Additionally, we know that leaky vaccines and continued spread may cause greater pathogenicity.
This is NOT supported by evidence, except in the completely silly sense that the virus "may" do anything, if it is allowed to continue existing.
If we partially vaccinate, SARS-CoV2 "may" evolve legs and do a little dance...but it probably won't (...and for that matter, it probably will hit an upper limit on transmissibility as well. But now I am speculating, if only in an evidence-based manner.)
I provided source evidence documenting an example of the mechanism and result of what I'm saying. Get back to me when you can provide a source example case of a virus evolving legs and doing a little dance and then we can consider the probabilities equivalent.
You provided a source showing that a chicken virus escaped selective pressure, in chickens, grown in a lab. Let's not overstate the relevance of your "evidence" to SARS-CoV2 amongst the human population.
But as I said, there's nothing terribly surprising about the idea that pathogens mutate to escape selective pressure. It's right out of biology 101. It would be tremendously surprising if those pathogens became more virulent, which is what you're trying to claim.
So let's be clear: the claim is that the virus can mutate, therefore, any particular outcome is equally likely?
If I speculate that the virus will mutate into a hemorrhagic fever, like marburg or ebola, is that reasonable?
If I speculate that the virus will lose its pathogenicity, is that reasonable?
(hint: all of our best data suggests that the IFR of the Delta strain is considerably lower than previous strains: https://assets.publishing.service.gov.uk/government/uploads/...)
There's obviously a limit to how much you can speculate about "continued change". At some point, it just becomes a scary story.