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Lots of wild deer are getting SARS-CoV-2. Scientists say this could be a huge problem


Scientists have evidence that SARS-CoV-2 is widely circulating in deer across the U.S. Researchers say the findings are concerning and could have vast implications for the long-term course of the global COVID pandemic. NPR's Michaeleen Doucleff explains.

MICHAELEEN DOUCLEFF, BYLINE: Early on in the pandemic, scientists were looking to see what other animals might be susceptible to SARS-CoV-2. And it turned out white-tailed deer were high up on the list because it looked like the virus could easily infect their cells. So Vivek Kapur decided to pair up with a program in Iowa that was already surveilling diseases in deer there. He's a veterinary microbiologist at Penn State University. He and his colleagues tested about 300 deer for SARS-CoV-2 infections, including roadkill.

VIVEK KAPUR: As well as the free-living deer during hunting season where deer are hunted.

DOUCLEFF: What Kapur and his colleagues found left them dumbfounded.

KAPUR: It was actually quite stunning to us, and we were very surprised at getting a - such a high number of positive samples.

DOUCLEFF: Throughout 2020, about a third of the deer they tested were infected with SARS-CoV-2. During the COVID surge last winter, that value skyrocketed. About 80% of the animals tested positive.

KAPUR: These are actually looking for signatures of the virus themselves. So that means that at that particular point in time, there was a very large number of deer that had active infection with this virus.

DOUCLEFF: These findings suggest that the coronavirus spread explosively through the white-tailed deer population in Iowa - like wildfire on the prairie. The prevalence of the virus is about 50 times that in people.

Suresh Kuchipudi is a veterinary virologist at Penn State and also contributed to the study. He says with an infection rate that high in Iowa, deer across North America are likely getting infected, too, which is tens of millions of animals.

SURESH KUCHIPUDI: They can be infected. They transmit virus among themselves. And there is evidence of antibody detection in deer in wild settings in multiple states of the U.S.

DOUCLEFF: OK. Now, at first blush, this news may not sound that bad. The virus doesn't make the animals sick, and it's easy to social distance with deer. But if you dig a little deeper into the science...

LINDA SAIF: It's very concerning to me.

DOUCLEFF: That's Linda Saif. She's a virologist at the Ohio State University. She says the concern is that deer could become what's called a reservoir for SARS-CoV-2 - that is, they could carry the virus around indefinitely.

SAIF: The question is, can it spill back from deer to humans? We don't know that yet. But if that's possible or if they could transmit it effectively to grazing livestock, then, obviously, this is a concern.

DOUCLEFF: Saif said the virus could also evolve inside the animals, possibly creating more dangerous variants. Scientists have already found a similar scenario can occur in minks. The virus can mutate in those animals and then go on to infect people.

SAIF: If the virus persists in deer, it can keep changing and emerging in deer. So now we've got, you know, a new potential reservoir host that we have to monitor.

DOUCLEFF: Finally, Suresh Kuchipudi at Penn State says that if deer do become a reservoir for SARS-CoV-2, it pretty much dashes any hopes of the U.S., and therefore the world, eliminating the virus.

KUCHIPUDI: If the virus has opportunities to find an alternate host, that will create a safe haven for the virus to continue to circulate.

DOUCLEFF: In the short term, Kuchipudi says hunters should take extra precautions, such as wearing gloves and masks around white-tailed deer to keep them from getting infected themselves.

Michaeleen Doucleff, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

Michaeleen Doucleff, PhD, is a correspondent for NPR's Science Desk. For nearly a decade, she has been reporting for the radio and the web for NPR's global health outlet, Goats and Soda. Doucleff focuses on disease outbreaks, cross-cultural parenting, and women and children's health.