Research Shows Covid Is Rampant Among Deer Who Have Been Infected By Humans

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Humans have infected wild deer with Covid-19 in a handful of states, and there’s evidence that the coronavirus has been spreading among deer, according to recent studies that outline findings that could complicate the path out of the pandemic.

Scientists swabbed the nostrils of white-tailed deer in Ohio and found evidence that humans had spread the coronavirus to deer at least six times, according to a study published last month in Nature.

About one-third of the deer sampled had active or recent infections, the study says. Similar research in Iowa of tissue from roadkill and hunted deer found widespread evidence of the virus.

The research suggests that the coronavirus could be taking hold in a free-ranging species that numbers about 30 million in the U.S. No cases of Covid spread from deer to human have been reported, but it’s possible, scientists say.

It’s a reminder that human health is intertwined with that of animals and that inattention to other species could prolong the pandemic and complicate the quest to control Covid-19.

Widespread, sustained circulation of the virus in deer could represent a risk to people if mutations in deer create a new variant. A population of wild animals harboring the virus could also retain variants that are no longer circulating among humans now and allow them to return later.

“The sheer possibility that these things are happening and it’s unknown makes this very unsettling,” said Suresh Kuchipudi, a virologist at Pennsylvania State University. “We could be caught by surprise with a completely different variant.”

Early in the pandemic, scientists grew concerned that the virus could jump from humans to other animals. One study found many mammals with receptors that could allow the virus to bind in their cells, with deer among those at high risk.

They began to investigate.

First, in a laboratory study, researchers spritzed four fawns’ noses with infectious coronavirus to test whether the virus could infect them. They also took two uninfected deer into the same room, keeping them separated with a plexiglass barrier that didn’t reach the ceiling.

“We had four inoculated animals and two contact animals. Everybody got infected and shed significant amounts of infectious virus. That was a surprise,” said Diego Diel, an associate professor of virology at Cornell University, who helped lead the research.

The deer most likely shared the virus through nasal secretions that traveled over the barrier by air, he said. The infected deer didn’t exhibit noticeable symptoms.

Deer often travel in herds and touch noses, making transmission a concern.

So federal scientists tested blood samples of wild deer in Illinois, Michigan, New York, and Pennsylvania. They eventually tested 624 samples, finding that about 40 percent of samples that were collected last year had antibodies that suggested past infection.

The latest studies provide evidence of active and recent infection.

In the peer-reviewed Ohio State University study, 35.8 percent of 360 free-ranging deer tested positive through nasal swabs. The researchers were able to culture the virus for two samples, meaning they could grow the live virus.

And after they reviewed genetic relationships among viruses from 14 deer, “we’ve got the evidence we have deer-to-deer transmission occurring,” said an author of the study, Andrew Bowman, an associate professor of veterinary preventive medicine at Ohio State University. The researchers found six mutations in deer that are uncommon in people.

A preprint study led by Kuchipudi of Penn State found the coronavirus in lymph nodes of 94 of 283 deer that were hunted or killed by vehicles in Iowa in 2020.

Both studies suggest that the virus spilled over from humans to deer several times in several places. The common viral genomes circulating in humans at the time were also circulating in deer, the studies say.

The research suggests that the coronavirus could be taking hold in a free-ranging species that numbers about 30 million in the U.S. No cases of Covid spread from deer to human have been reported, but it’s possible, scientists say.

It’s a reminder that human health is intertwined with that of animals and that inattention to other species could prolong the pandemic and complicate the quest to control Covid-19.

Widespread, sustained circulation of the virus in deer could represent a risk to people if mutations in deer create a new variant. A population of wild animals harboring the virus could also retain variants that are no longer circulating among humans now and allow them to return later.

“The sheer possibility that these things are happening and it’s unknown makes this very unsettling,” said Suresh Kuchipudi, a virologist at Pennsylvania State University. “We could be caught by surprise with a completely different variant.”

Early in the pandemic, scientists grew concerned that the virus could jump from humans to other animals. One study found many mammals with receptors that could allow the virus to bind in their cells, with deer among those at high risk.

They began to investigate.

First, in a laboratory study, researchers spritzed four fawns’ noses with infectious coronavirus to test whether the virus could infect them. They also took two uninfected deer into the same room, keeping them separated with a plexiglass barrier that didn’t reach the ceiling.

“We had four inoculated animals and two contact animals. Everybody got infected and shed significant amounts of infectious virus. That was a surprise,” said Diego Diel, an associate professor of virology at Cornell University, who helped lead the research.

The deer most likely shared the virus through nasal secretions that traveled over the barrier by air, he said. The infected deer didn’t exhibit noticeable symptoms.

Deer often travel in herds and touch noses, making transmission a concern.

So federal scientists tested blood samples of wild deer in Illinois, Michigan, New York, and Pennsylvania. They eventually tested 624 samples, finding that about 40 percent of samples that were collected last year had antibodies that suggested past infection.

The latest studies provide evidence of active and recent infection.

In the peer-reviewed Ohio State University study, 35.8 percent of 360 free-ranging deer tested positive through nasal swabs. The researchers were able to culture the virus for two samples, meaning they could grow the live virus.

And after they reviewed genetic relationships among viruses from 14 deer, “we’ve got the evidence we have deer-to-deer transmission occurring,” said an author of the study, Andrew Bowman, an associate professor of veterinary preventive medicine at Ohio State University. The researchers found six mutations in deer that are uncommon in people.

A preprint study led by Kuchipudi of Penn State found the coronavirus in lymph nodes of 94 of 283 deer that were hunted or killed by vehicles in Iowa in 2020.

Both studies suggest that the virus spilled over from humans to deer several times in several places. The common viral genomes circulating in humans at the time were also circulating in deer, the studies say.

Researchers can’t say for sure how the deer are becoming infected or whether the virus will persist in the species. Deer, ubiquitous in many U.S. communities, are among the most abundant large mammals in the country.