For people looking for an accessible writeup on the coronavirus mutational landscape, I can recommend this Reuters article that came out today. It has a lot of good information in it, and a lot of very well-made graphics to show what’s going on. Past blog posts on this subject are here, here, here, here, and here.
And what’s going on, of course, is that the virus is mutating. It’s what viruses do. They don’t have a lot of overhead for lots of redundant error-checking machinery (although some have more of that than others), and honestly, total fidelity is not really an evolutionary advantage. A little sloppiness in copying the genetic material gives a more diverse population of viruses, with members that are more likely to be able to meet new threats or take advantage of new opportunities for infection. You would expect, over time, the viruses that can do a better job of that to be more represented. And remember, evolutionary time works different for viruses than it does for us. They turn around a new generation so quickly and in such huge numbers; they’re mashed down on fast-forward constantly.
So the mutational background is constant, but it’s important not to make the teleological error of picturing this all as being due to calculation, with the virus outwitting its adversaries. It can look like that, for sure, but it’s just millions of random chances spewing out everywhere – some work, some don’t, and what we see is the residue of some stuff that worked. You’ll see from the Reuters article that strains with a Gly in position 614 (the D614G one and its further offshoots) have become much more prominent. And those do seem to have a bit of an advantage in the binding behavior of the Spike protein – but if you look at some other situations around the world, you can see that other factors are at work. Singapore, for example, showed a lot of low-frequency mutations for a long time, apparently because these were showing up in foreign worker dormitory buildings which were then hit with vigorous quarantine measures. South Korea, for its part, had a lot more “V” family strains for a while due to a single superspreader event, which stood out against the country’s generally strong response. So there are a lot of extraneous factors and sheer accidents mixed into the data landscape.
The good news continues to be that none of the mutations studied so far in the general population seem to be able to evade the antibodies raised by the current vaccines. That doesn’t mean that it can’t happen – and as we start putting selection pressure on the virus by vaccinating people we’ll have to keep a close eye out for anything like that developing. But then we have to consider transmission. If an antibody-evading form of the virus also becomes harder to catch, well, it’s going to be less of a worry. But if we were to start doing a better job at not spreading the virus in general, that would be sort of nice, because that would reduce the chance that any nasty mutated forms get any kind of traction in general. If some sort of supervirus mutation occurs in a single patient who doesn’t then get close enough to other people for it to spread, then it’s a tree falling in a forest that doesn’t make much of a sound.
It’s all a race between several different factors. But here in the US we have so many people infected (and so much transmission going on) that frankly we’re making ourselves vulnerable to any more dangerous mutations that might crop up. In fact, if something like that were to emerge, the odds are better that it would do so here, from what I can see. We’re giving the virus every opportunity to reproduce and for the subsequent viral variations to then go out and try their luck infecting lots of other people. Vaccinating enough people quickly enough would interrupt these processes, and so would doing the sorts of public health measures that we’ve all been hearing about for months. But the first is going to depend on vaccine supplies, logistics, and public acceptance, and the second, well, look around you, si monumentum requiris.
It’s good news that no profoundly worse mutations have spread so far, and that might be a sign that they’re not so easy to come by. But then again, this virus has a relatively short acquaintance with human beings, so I think it would be prudent to assume that there are still a lot of things that we don’t know about its interactions with us. Let’s do everything we can to give it as few chances as possible.