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Comment by DoingIsLearning | Hacker News Reader

Non virologist naive question, if we apply all these measures targeting SARS-COV2 and it also creates a massive negative pressure on flu viruses, is there a risk that this applies an adaptive pressure to select for a future uber infectious new flu strain?

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I don't see any reason to expect it would. Summer months, for example, already apply a strong negative pressure on the flu virus (that is, we have a flu season), yet we have not seen a year-round flu.

Diseases always face selection pressure to spread more easily and rapidly. When that selection pressure is caused by broad factors like "people aren't congregating together," it's hard to imagine how any simple evolution could overcome that barrier.

Covid itself is instructive here. Some of the variants of concern are more transmissible than the originally-distributed variant as of March of last year, but those mutations don't uniquely overcome masks or social distancing. They would have always result in a more transmissible virus (because SARS-CoV-2 appears to be a zoonotic virus not originally perfectly-adapted to humans), and we are seeing them now because each infected person is a new roll of the mutation dice.

Applying that lesson to the flu, the less prevalent the virus the less likely we are to see variations, not more. Alas, for influenza itself we always have the asterisk that we regularly see new variations cross to humans from animal reservoirs, so we're unlikely to eliminate it through only (nonpharmaceutical) human-health measures. (It'd be nice to get a universal flu vaccine, though.)

> yet we have not seen a year-round flu.

We had. And it may have killed 3% to 5% of the world population in about 2 years: https://en.wikipedia.org/wiki/Spanish_flu

That's also why we are so afraid of this one and constantly monitor it: https://en.wikipedia.org/wiki/Avian_influenza

My layman understanding is that it doesn‘t work that way. Less spread = less chance of mutation = less chance of uber infectious new flu strain.

It's potentially the opposite. Say you have a population of 1000. If one person infects ten others. Then its going to be 3 generations before 1000 are infected and full immunity is reached.

We go for a suppression strategy instead.If 1 person infects 1 other person (as we seem to be trying to achieve with corna) it is going to take 1000 generations before full immunity is achieved. There is going to be far more chance of mutations in 1000 generations of viral replication than in 3 generations.

That is a really interesting thought. But isn‘t the chance of mutation per viral replication (which happens million-fold in each human per infection) and not per human? What I meant was that if we contain the virus to only ever get 1% of the population sick then there is a lower chance of mutation than if it gets 70% sick.

If everybody has had the disease, what's the purpose of having full immunity?

However, I think this is right in one sense: an implicit or explicit strategy of keeping R0 as close as possible to 1 would be the strategy with the highest risk of significant mutations, as we have seen.

UK government ministers literally stated this to be their strategy.

It was just an example to make the theory easier to understand.

Your second paragraph assumes that a suppressed virus will not go extinct. If the suppression is effective, with eg. vaccines it can be done with quickly, with no higher chance of mutations.

> If the suppression is effective

Comparing places that didn't lock down to those that did I think its fair to say that the strategy has not been effective.

Where people weren’t constantly battling the decisions, lockdowns were quite effective. The problem is that without a very strict but short lockdown you will get into this semi-lockdown that is hardly effective and thus just prolongs everything. But the answer never is “just do whatever you want”.

No they weren't we have had close to a year of them here in Spain, and the first few months were ridiculously strict.

It's unlikely. Most of the major "uber infectious" influenza strains don't emerge via ordinary mutation (antigenic drift) but the reassortment of two viral genomes that have infected the same host (antigenic shift). Given pigs and wild birds aren't social distancing, there's no reason to believe there's a distinctly high amount of additional pressure one way or the other.

Chance of mutation depends mostly on the number of infected —- applying antibiotics is problematic because it is a repeated process, and the net amount of cell divisions is huge with iterating killing and “letting go”. With effective and strict measures, the pandemic could quickly die out with basically minimal chance of a super-mutation.

The current some half of the world somewhat protected, while other parts are breeding grounds is a pretty bad state to be at, with a potential mutation turning up and endangering the protected people as well again.

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