We’re all getting something that I don’t think any of us wanted: another less in real-time virology and epidemiology. I’m referring to the puzzling recent outbreak of monkeypox, which is getting more and more headlines. Add that to the rise in hepatitis cases in children, on top of the continuing (damn it all) coronavirus pandemic, and we really have a lot more virus news to work through than usual. I’m not sure what the optimum level is, but this ain’t it.
A quick look at the monkeypox virus, then. For starters, it is in no way related to the coronavirus as a virus – totally different part of the landscape. Monkeyvirus is a DNA virus (not an RNA one like corona), and it’s in the same broad group as variola (smallpox), cowpox, and vaccinia. In fact, smallpox vaccination itself is rather effective against monkeypox infection (about 85%), but fewer and fewer people have been vaccinated against the now-extinct smallpox virus (a triumph of medical science and public health, let us not forget), and those of us who were are of questionable immune status. It’s been a while! The virus appears to be endemic in West and Central Africa, and there have been outbreaks in that area before. For that matter, there have been outbreaks in other parts of the world, too – monkeypox can be carried in a number of mammalian species, and a 2003 outbreak in the Midwest traced back to people handling prairie dogs purchased from pet stores (!), which had in turn been infected by Gambian pouched rats (!) imported from Ghana. 77 people eventually came down with the disease that time, all from prairie dog contact. We don’t actually know the real animal reservoirs for the virus in Africa; there may be several. The viruses in this genus enter cells by binding to glycosaminoglycan molecules on the cell surface, followed by endocytosis. DNA viruses like these are a *lot* larger and more complicated than RNA viruses like corona. Coronaviruses are among the largest RNA viruses known, at about 30,000 base pairs, but things like monkeypox are up over 200,000 bp. They have both an RNA polymerase and a DNA polymerase, and their gene expression/protein production goes through several stages, with characteristic “early” and “late” proteins, with the structural proteins for making new virion particles showing up near the end.
Monkeypox itself (the disease) is fortunately not in the same league as smallpox. It causes extremely similar skin lesions (although very few people by now have ever seen anyone with actual smallpox), but people generally recover over a period of a few weeks with supportive medical care. No one died in the 2003 outbreak in the US. The previous record outbreak in the human population was in 1996-97 in the Congo – several hundred cases were reported, with a small number of fatalities (all of them young children, from what I can see). You would of course also expect immune-compromised people to be at greater risk, both of catching the disease and for a more severe course. It’s not particularly contagious – the virus needs close physical contact and/or outright broken skin. People butchering wild animals in West Africa are at risk, as are people living with an infected person (extended face-to-face interactions), and sexual contact is pretty good at transmission as well.
But the current outbreak is odd, there’s no way around that. This is the first time that we’ve seen real human-to-human transmission outside of Africa, for one thing. The way that the virus has cropped up in several countries more or less simultaneously makes it clear that that’s what is going on – there’s no crate of prairie dogs or Gambian pouched rats going around to all these places. The current virus is being sequenced in depth, as you’d imagine, and people are poring over the data right now and comparing it to “classic” monkeypox sequences to see if this a new variant, perhaps with enhanced transmissibility. So far there are no glaring signs of that, but this work is very much ongoing; it’s just too early to draw any conclusions. Similarly, it does not appear that this current outbreak is leading to any more severe consequences than usual – so far – but it’s not clear that it’s leading to any fewer ones either. That’s also a work in progress.
The EU is out with a new document that warns (among other things) that this zoonotic spillover could spill over yet again from humans to other mammals in Europe, potentially making monkeypox endemic there as well. That’s a real concern, since we know the disease can be carried by a variety of small mammals – but what we don’t know is the likelihood of humans passing it on to them (or of the disease getting established among their populations in the wild). Yet another set of questions to be cleared up!
Overall, I would say that this is in the don’t-panic-but-keep-a-close-eye-on category. We have not had a monkeypox event like this before, and while it’s unlikely to turn into a global pandemic itself, it’s not impossible, either. We just really do not need another viral burden spreading around, nor another big public health concern. The best case is that this outbreak damps down, the infected people recover smoothly, and we go back to not reporting weirdo cases of monkeypox in places it’s never been seen before. The worst case is that it becomes endemic in those places and it becomes an ongoing, more-or-less-impossible-to-eradicate disease that keeps showing up here and there because it’s sitting around in squirrels, mice, what have you. The US could certainly become one of those places, because we’ve seen at least three cases here and there are very, very likely to be more that we haven’t realized yet. Even in that case, it could be a sporadic thing that showed up in a few cases some years, none at all in others, and so on. But if this is a more human-to-human-transmissible form of the virus, which I very much hope is not the case, we’re going to have to rethink that.
