A new study shows that the alpha and gamma variants of the coronavirus continued to spread and evolve in white-tailed deer even after it stopped spreading widely among people.
Whether deer are still circulating is unknown. “That’s the big question,” said Dr. Diego Dial, a virologist at Cornell University and author of the study, which was published Tuesday in the Proceedings of the National Academy of Sciences.
But the findings, which are based on samples collected up to December 2021, provide more evidence that deer could be a reservoir of the virus and a potential source of future variants, which could seep back into human populations.
“This is a very large wildlife population in North America that has continuous and very intense contact with humans,” Dr. Dial said.
Previous studies of deer have suggested that humans have repeatedly introduced the coronavirus into populations of white-tailed deer in the United States and Canada and that deer can spread the virus to each other. Scientists aren’t sure how people are passing the virus to deer, but they speculate that it may happen when people feed deer or deer and encounter human waste or garbage.
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- A reservoir of old forms?: New research shows that the alpha and gamma variants of the coronavirus continued to spread in white-tailed deer, even after they had stopped spreading widely among people.
The scale of the risk posed by deer to humans is not clear. Scientists have documented a case that likely resulted from deer-to-human transmission in Ontario, and they note that hunters and others who have regular contact with the animals could potentially catch the virus from them.
For the new study, Dr. Dial and colleagues analyzed nearly 5,500 tissue samples collected from deer killed by hunters in New York State from September to December in 2020 and 2021.
During the 2020 season, only 0.6 percent of samples tested positive for the virus, with that figure increasing to 21 percent during the 2021 season.
Genetic sequencing showed that three different variants of the antelope — alpha, gamma and delta — were present in all deer during the 2021 season.
At the time, Delta was still prevalent among the human inhabitants of New York. But Alpha and Gamma had practically disappeared, especially in rural areas of the state where infected deer were found.
The scientists compared the genomic sequences of viral samples found in deer with those collected from humans. In deer, all three forms had new mutations that distinguished them from the human sequences. The researchers found that the alpha and gamma samples from deer diverged more significantly from the human sequences than did the delta samples from deer.
Together, the results suggested that Alpha and Gamma were probably circulating among deer and accumulating new mutations for months, experts said.
“This supports the argument that deer may be maintaining lineages or variants that are no longer spreading to humans,” said Dr. Suresh Kuchipudi, who was not involved in the new research.
The finding not only raises concerns that deer could be a source of new coronavirus variants that could spread back to people; He said it also raises the possibility that the virus could evolve in ways that pose a greater risk to wild animals. “It can also become an animal health problem,” said Dr Kuchipudi.
The study highlights the need for continuous monitoring of wild deer populations, said Dr. Kuchipudi and Dr. Dayal. Doctor. Dial and his colleagues are preparing to analyze deer samples from the 2022 hunting season to determine whether the virus is widespread among deer and which variants are circulating.
The Centers for Disease Control and Prevention recommends that deer hunters take a number of basic precautions to reduce the risk of infection, including wearing a mask when handling game and washing hands thoroughly afterward.