[simo7]

True, there's no selective pressure for it to become less lethal.

But I wonder: isn't a random mutation unlikely to improve on any of its profiles (transmissibility or lethality)? If so a more transmissible virus is unlikely to also be more lethal.

What if (not sure) a random mutation actually tends to do slightly worse? Then more transmissible viruses tend to be less lethal over time.

Sure we still get more lethal mutations from time to time, but the more transmissible ones are the ones which win out.

[IneffablePigeon]

I'm no expert but my understanding is that unfortunately there is some correlation between transmissibility and severity of disease, because one of the ways it can become more transmissible is to reproduce in your cells faster so that you shed more virus particles. This also means it takes over quicker and your immune system has less time to respond before it does lots of damage.

Whether that outweighs the randomness you describe I don't know. Maybe nobody knows for this virus?

[simo7]

Well if the two events (improved transimissibility and improved lethality) are not independent as I assumed then it's certainly bad news.

I also heard the opposite thesis btw, higher transimissibility might sacrifice something in terms of lethality. Like you can't really add much as I'm not an expert.

[wbsss4412]

The people have dramatically altered their behavior on a global scale (on average anyways) because of COVID’s lethality. There is absolutely selective pressure in that dimension.

If the lethality of Covid were to drop to seasonal flu levels there wouldn’t be anywhere near the amount of research into medical interventions nor would we feasibly maintain our current levels of public health interventions.

[simo7]

Don't really get your point.

> The people have dramatically altered their behavior on a global scale (on average anyways) because of COVID’s lethality. There is absolutely selective pressure in that dimension.

This reads to me: "Covid is certainly more lethal than the average flu, therefore is undoubtedly getting less lethal" (effect of selective pressure). It doesn't make much sense.

> there wouldn’t be anywhere near the amount of research into medical intervention

Right, how's that has to do with whether there's selective pressure or not?

It almost feels like you are attributing a different meaning to "selective pressure", but cannot understand which one.

[wbsss4412]

You seem to misunderstand what selective pressure is.

Selective pressure is anything that disrupts replication. If people take measures to prevent spread of a disease that’s literally selective pressure. I don’t understand what is confusing about that concept.

[simo7]

I think you're too quick at making assumptions which are not correct unfortunately. Let's recap:

> there's no selective pressure for it to become less lethal.

> If people take measures to prevent spread of a disease that’s literally selective pressure.

How trying to slow down its spread can "force" it to become less lethal?

The only possible answer is that lower lethality gives it more time to spread around right?

It turns out Covid has a long incubation period, in fact plenty to use the host to infect other people.

Tl;dr: Given the length of the incubation period a less lethal virus would not gain much in terms of its ability to spread. That's the thesis I'm hearing.

[mro_name]

> random mutation unlikely to improve

indeed, but subsequent success or failure does. Mutation and selection. Mutation prepares the pool to sieve the successful ones.

[simo7]

Yes my point is, when you do improve one (transimissibility) you probably did not improve the other one (or even got worse at it).