Viruses can't really "adapt" to "not being spread". It's not quite zero, I suppose we could hypothesize some superior ability to survive on a surface for some period of time or something, but there's not much they can do about it.

Bacteria would have more options, since they're so much more complex. Viruses just don't have much they can do.

> Viruses can't really "adapt" to "not being spread".

Of course they can. We have this pandemic because a coronavirus became highly transmissible.

Perhaps I was not clear. A virus can't "adapt" to not being physically presented to its potential host. It can't "adapt" to "being blocked by a mask" or "the person I infected intelligently self-isolating and thus I can't spread any farther". Even if you could hypothetically draw out genetic changes that would permit it, it would require substantial changes to evolve all at once.

Not really, no. There is a 99.999% chance that the virus was just as infective if not more in bats or pangolins or whatever, and simply adapted to humans.

These mutations are the virus finishing its adaptation to humans. It will eventually end up at a local maxima, just like, say, measles did.

It most likely jumped the species barrier.

They mutate, and mutations more successful in causing infections cause more infections and become dominant.

There are many ways for this to happen, some of which covered in this thread - changes in the surface presented to the host, more viral load produced and expelled by an infected host earlier being some obvious ones.

Some potential methods that have occurred with other diseases in the past include additional methods of infecting hosts (from prior versions), such as viral envelopes that can insert against additional types of cells, or changes to the way the virus hijacks cell replication machinery to produce products that are better at hiding what is going on to the immune system.

Those all involve the virus reaching the host.

The virus can't "evolve" its way around not reaching the host very well. Evolution isn't magic. The virus can't "evolve" teleportation or an immunity to high-energy electromagnetic radiation just because it would be really useful to it if it could. It can't just "evolve" its way around masks very well.

As I said, bacteria have at least more options, though they face the same physical constraints everything else in the universe does. Viruses don't really have many options. They are very simple.

> The virus can't "evolve" its way around not reaching the host very well.

That's what "becoming more contagious" is. Obviously, no one in a submarine is getting it until it docks, but when you're dealing with 95% effective masks, tests that have a 20% false negative rate, and surfaces not being an effective vector, there are still plenty of opportunities to reach the host, and we're selecting for viruses that were able to. Someone else mentioned measles; sars-cov2 is nowhere near that contagious, but it means there's room for it to get worse.

Most of the masks people are wearing are also nowhere near 95% effective - cloth masks are more like 70%. Helpful, yes! Solid protection? Far from it.

COVID-19 had a measured replication rate before measures were taken in NYC of ~ 6. Measles is ~ 11 (and the most infectious known airborne virus). New variants are supposed to be between 50-70% more infectious than 'baseline' COVID, though it isn't clear how solid that data is, or how exactly it is being computed.

That could put it at a 'with no social changes/baseline behaviour in manhattan' at a replication rate of ~9 to ~10. Which is damn close to measles.

Lockdowns, social distancing, face masks will reduce this quite a bit in reality (and have - the measured R value is in the 1.1-1.2ish range in most areas now) - but increases in infectivity will require stepping up countermeasures to contain it, or a massive rollout in vaccines to stamp it out before a variant that the vaccine doesn't prevent against exists.