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Concerns about coronavirus transmission between humans and animals

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Experts are concerned about the coronavirus spreading from humans to animals, and the implications of infected animals spreading the virus unchecked. Author and journalist David Quammen spoke to Anne-Marie Green and Vladimir Duthiers on CBSN about why the U.S. wasn't more prepared for a pandemic to emerge and how the virus can spread between species.

Video Transcript

VLADIMIR DUTHIERS: While the world is racing to get people vaccinated against the coronavirus, scientists believe the virus is spreading from people to animals. A recent op-ed in "The New York Times," "And Then the Gorillas Started Coughing," takes a look at the implications of human to animal transmission. David Quammen wrote the piece. He's an author and a journalist who's written books about different viruses and how they spread, and he's joining us now to talk about it.

David, thank you so much. You write about how gorillas at the San Diego Zoo started coughing, which was a sign that they were infected with COVID-19. Tell us about this case. And how were the gorillas exposed? And, I guess, what does the transmission tell us about this virus and our mitigation measures?

DAVID QUAMMEN: Yes, well, I'll take the second question first. It tells us that this virus can go back and forth between humans and other animals. The case in San Diego began in early January. They have a group of eight gorillas. Some of them started coughing. And they had taken precautions.

The zookeepers-- the people who dealt with the gorillas-- were wearing personal protective equipment, distancing themselves as much as they could. Still, some of the gorillas started coughing. They tested fecal samples, they found evidence of the COVID-19 virus, SARS-CoV-2. And then, there was one elderly male gorilla named Winston. My understanding is that they anesthetized him and took blood samples from him, and he tested positive for the virus.

The good news is that all eight gorillas are doing fine now. But it was a warning shot. It was a tremor, telling us-- and there are evidences of this-- that this virus can go from humans into other animals and potentially establish itself in wild animals, from which it could spill eventually back into humans.

ANNE-MARIE GREEN: And so speaking of a warning, you actually wrote a book that came out in 2012. And on the back cover, you basically wrote about this. You say plainly, the next big human pandemic is likely to be caused by a zoonotic virus, one that jumps from a wild animal to infect a human host. You were right. So you saw it coming, I presume others saw it coming. Why did this take the world by surprise the way it did?

DAVID QUAMMEN: Well, you're right that others saw it coming. I only saw it coming because I was spending time with the disease scientists who study this field. And I was traveling with them, and they were researching this. And they could even tell me that-- 10 years ago-- that the next pandemic would not only be caused by a virus coming from a wild animal, but it might well be caused by a coronavirus coming from a bat. That was known.

The sirens were blaring in the scientific literature. But political leaders found it undesirable-- particularly the political leader that we had for four years-- undesirable to spend the money, and the effort, and the political capital to have us adequately prepared for this. Other countries were better prepared because of the SARS experience in 2003. But SARS in 2003 did not wake the US up the way it woke up, for instance, Hong Kong, Singapore, and China.

VLADIMIR DUTHIERS: So concerns over a mutated version of the coronavirus linked to mink fur farms led Denmark to cull millions of mink last year. And we've seen so many variants of COVID-19 cropping up. How is it that these viruses evolve so quickly and in different ways?

DAVID QUAMMEN: Well, this-- this coronavirus and coronaviruses generally belong to a group of fast evolving viruses known as the single stranded RNA viruses. That simply means that when they replicate themselves, they make mistakes. Coronaviruses also have the capacity to switch sections from one to another. You have two different strains of coronavirus infect a single individual. So they are fast evolving viruses. They are mutating, but it's a truism to say that a virus is mutating. A virus is always mutating when it replicates in a host.

But those mutations are the raw material for Darwinian natural selection. And the more mutations, the greater the chance that the virus will evolve in order to adapt, to become better transmissible from one individual to another, perhaps to evade the immune system better, perhaps even to evade vaccines better. So mutations are always there. But Darwinian natural selection is what uses them, in some cases, to make a more dangerous, more effective, more successful virus.

ANNE-MARIE GREEN: I think it was maybe sort of midway through last year, there was an article that popped up about how cats could get the coronavirus. And I remember thinking at the time, this is just more fuel to the fire for people who think that all cats are jerks, because I happen to like cats and dogs. But it is sort of interesting that cats seem to be more vulnerable to this virus than dogs are. Why are some animals more susceptible than others?

DAVID QUAMMEN: Well, this virus has done something ingenious. It has adapted to enter the cells of its host using a particular receptor on the cells, the thing that it catches hold of and allows it to enter the cell. It's called an ACE2 receptor. It's a protein on the surface of certain cells that are in our respiratory tract, in our organs. It's a protein that performs a function. It helps to regulate blood pressure, and therefore it is common in mammals. It's common, particularly, in the cat family.

It's common in the family that ferrets and mink belong to. It's common among primates. It's not so common among dogs. But this ability to use that particular handle, that particular receptor to get into cells, the ACE2 receptor is what has made this virus not just dangerous to humans, but capable of spreading to-- to the mink family, to the cat family, less so to the dog family. Don't worry about your cat giving you COVID-19. You're more likely to give COVID-19 to your cat. But your dog is less likely to receive it or to give it.

ANNE-MARIE GREEN: Well, that's good to know because cats find it very difficult to wear masks as much as they should.

VLADIMIR DUTHIERS: They don't sit still for it.

ANNE-MARIE GREEN: Just injecting a little bit of humor. I know this is a very serious topic. [CHUCKLES] Dr. Quammen, thank you-- I'm sorry, David.

DAVID QUAMMEN: We have dogs and a cat in this household, too. We're not concerned.

ANNE-MARIE GREEN: OK. Well, that's good. That's good to know. David Quammen, thank you very much, appreciate it.

DAVID QUAMMEN: You're very welcome.