There’s a Covid-19 epidemic in deer. It could come back to haunt us.

“How the virus spreads among wildlife is a black box that scientists try to peer into through the tiniest of pinpricks. But what they do know is that when the coronavirus establishes itself in wildlife, it creates for itself a sort of insurance policy. We may be able to get the pandemic among humans under control, but the virus is likely to lurk in other species, making it that much harder to monitor and defeat.

The spread of SARS-CoV-2 in wildlife is not the most pressing issue of the pandemic right now. Humans are still catching the virus from each other and dying from it. Still, these wildlife risks, if they are realized, could have serious consequences. Scientists want to be vigilant about dangers that could emerge from the wilderness.”

“Infections have turned up in cats, dogs, lions, tigers, pumas, ferrets, mink, certain rodents, snow leopards, and others. The CDC even has guidelines to protect pets from Covid-19. When a virus jumps from animals to humans and then back to animals, scientists call that spillback.

Most of these infections in animals appeared to be self-contained. An infected house cat presumably stays in the house when infected — it doesn’t start a chain of transmission. “They were all isolated cases,” Suresh Kuchipudi, a Penn State infectious disease researcher who collaborated with Kapur, says of known cases in animals.

The deer infections were different. “This is first time that a completely free-living animal species in the wild has been found to be infected, and that infection is widespread,” Kuchipudi says.

How the deer got infected in the first place remains a mystery, but researchers believe the outbreak came from humans. The virus circulating in the deer had similar genetic sequences to the virus circulating in humans at the time that they got it.”

“Whatever happened to start the deer outbreaks, it appears to have happened many times. The genetic analysis in the PNAS paper finds evidence of several separate jumps from humans into animals. Further research needs to be done to identify the exact pathway, and hopefully to prevent the next leap.

Once the virus jumps into the deer, they are also spreading it to each other, the studies find. “There was not just human-to-deer spillover, but there was also deer-to-deer transmission, as evidenced by genomic changes that would confirm that,” Kuchipudi says.”

“The pandemic in humans is much more urgent than Covid-19 in animals. All of the scientists I spoke to agreed about that. The coronavirus is still killing thousands of people every day, and that’s the problem that should get the bulk of our attention and resources.”

“On the other hand, the scientists say they want more visibility into what’s happening in the animal world. “We need wildlife surveillance,” Olson says, meaning more testing of animals for coronavirus antibodies — a sign they have been exposed — or active infections. “We just don’t have the tools to begin to understand the system, to even start mapping what’s going to happen here, because our ability to see it is so opaque right now.””

“Covid-19 outbreaks in animals are not situations we can plausibly control. Rather, they’re something to monitor in case they start to look like pressing problems.”

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