We’ve learned time and again that animals can give diseases to humans. We’ve seen this happen with coronaviruses, the flu, Ebola — basically most major disease outbreaks in recent memory. But, of course, the reverse is true too: Humans can give viruses, including the novel coronavirus, to animals. FiveThirtyEight’s senior science writer Maggie Koerth wrote about this on the site earlier this week, and she joined PODCAST-19, FiveThirtyEight’s coronavirus podcast, to discuss her work further. The episode and a lightly edited transcript follow.
Anna Rothschild: So, to start off, which animals do we know can contract COVID-19?
Maggie Koerth: So, over the course of the last year, there’s been a lot of research on this. And some of it has been just naturalistic — this is a transference of SARS-CoV-2 that happened — some of it is stuff that’s coming from laboratory experiments on cell lines, and some of that is coming from direct animal experiments. But what we are sort of figuring out is that there are quite a few animals that actually are susceptible to SARS-CoV-2, to contracting COVID-19, from us. That includes your minks, and ferrets, kind of similar to those minks from Denmark that got COVID last year. You’ve got rabbits. You also have the cat family, so everything from lions and tigers to your domestic kitty cat living in your living room, are all susceptible to COVID. In fact, cats seem to get it pretty easily from us. You also have nonhuman primates. So this has been an issue for gorillas as well.
Anna Rothschild: So, just how sick do these animals get?
Maggie Koerth: Some of them get very sick. I mean, minks were dying from this, and some of them have very few symptoms at all. What we’ve seen sort of with the domestic cats, for instance, has been, you know, maybe a runny nose, but not necessarily even showing any symptoms, just carrying it around and transmitting it from cat to cat.
Anna Rothschild: So, this may seem like kind of a silly question. But if certain animals aren’t getting so sick, why should we worry so much about them actually contracting this disease?
Maggie Koerth: Well, to illustrate that, I will point back to the fact that Asian bats don’t necessarily get very sick with COVID-19. But they were carrying around all of these coronaviruses, including the precursor viruses to SARS-CoV-2. A population that doesn’t get very sick but gets this virus pretty readily is a population where a virus can begin to mutate and change and either jump back to humans or begin to make its hosts more sick and other hosts more sick.
Anna Rothschild: Right, it’s actually pretty similar to what we are saying about people who don’t get vaccinated. Just because the risk to you is fairly low — say, you’re young and don’t have any preexisting conditions — doesn’t mean that the virus can’t mutate inside of you if you get it and, you know, start off a cascade of new infections that are actually more dangerous.
Maggie Koerth: Right, every place that a virus has an opportunity to divide, to reproduce, is an opportunity for its genetic information to be copied. And every time your genetic information gets copied, well, that is where mutations happen. And most of the time those mutations honestly do not matter. But the way that evolution works is that sometimes they do.
Anna Rothschild: Do we have real-world examples — maybe not from COVID-19 but from past viral infections that have jumped from humans to animals — of the viruses kind of changing as they get passed back and forth between humans and animals?
Maggie Koerth: We do. Flu is actually really fascinating for this. And we know…