New canine coronavirus jumps to humans—without ever being diagnosed in a dog

Scientists have long known—and the public is learning—that coronavirus outbreaks aren’t rare, and it’s likely that we can expect a new one to pop up and jump from animals to people every 10 years or so.

In a new study spearheaded by scientists at Duke University, researchers detail how they found a novel canine coronavirus nobody had seen before. And they found it in a place they weren’t expecting—in humans.  

And it popped up three years ago, so it actually made the jump pre-COVID.

Researchers at Duke stumbled on it last year while testing nasal swab samples taken from 301 pneumonia patients—mostly children—at a hospital in Malaysia in 2017 and 2018. Eight of those samples (2.5%) came back positive for a previously unknown canine coronavirus.

Puzzled, the researchers sent the samples to Anastasia Vlasova, DVM, PhD, an animal coronavirus expert and assistant professor at The Ohio State University College of Veterinary Medicine, who was equally puzzled—until she decoded the genome.

Vlasova discovered that most of the genome was canine coronavirus. And by following the gene sequence, she also figured out that the new virus had likely infected cats and pigs first, then jumped to dogs.

And from dogs, it jumped to people. But how?

That’s not clear, but Vlasova told NEWStat that the genome contained a unique mutation—one that isn’t found in any other known canine coronavirus but is found in human coronaviruses. That mutation may be what helps the canine coronavirus infect humans.

Canine coronaviruses aren’t generally thought to infect humans, which was another surprise, but Vlasova said it’s not unknown: “I’m aware of at least two other studies that identified [similar] coronaviruses in human patients. . . . . [As in our study], these coronaviruses were identified in patients with acute respiratory illness.”

Ironically, Vlasova said this particular canine coronavirus has never been identified in a dog. And as far as the researchers know, the patients had no known previous exposure to dogs, so it’s possible they contracted it from other humans, although the researchers have no proof of that. But Vlasova downplays fears of further spread—the virus is still learning how to infect people. “Even if human-to-human transmission is possible, it’s unlikely to be very efficient.”

Research is ongoing. As the researchers write: “This is the first report of a novel canine-feline recombinant alphacoronavirus isolated from a human pneumonia patient. If confirmed as a pathogen, it may represent the eighth unique coronavirus known to cause disease in humans.”

NEWStat asked J. Scott Weese, DVM, DVSc, DACVIM, if the new coronavirus was a cause for worry. A contributing reviewer of the 2018 AAHA Infection Control, Prevention, and Biosecurity Guidelines, Weese writes about the topic on his blog, Worms & Germs. “It’s not a big concern since there’s no evidence it’s spread and these cases were from a few years ago,” he told NEWStat. “It’s more of a reminder that emerging disease threats are ever-present and probably increasing.”

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