Possible case of deer-to human Covid infection identified in Canada

Researchers say it is unlikely that the variant found in deer could bypass vaccines, but urge better monitoring of Covid in animals

Canadian researchers believe they have found the first-ever instance of a deer passing the coronavirus to a human, warning that broader surveillance of wildlife is needed to prevent further mutations from developing and spreading undetected.

In a paper published last week, but not yet peer reviewed, scientists say at least one case of Covid-19 in humans can be traced to a strain of the virus found in hunted deer.

Biologists have previously found white tail deer populations infected with Covid in northeastern regions of the United States, as well as central provinces of Canada. While deer aren’t typically seen as a species that can easily pass on the virus to humans, experts had nonetheless speculated that transmission was possible.

As part of their study, Canadian scientists took samples from hundreds of white tail deer hunted last fall in southwestern Ontario. After conducting nasal swabs and testing the lymph nodes of the deer, they found 17 of the 298 deer were positive for a “new and highly divergent lineage” of the coronavirus.

The virus bears little resemblance to strains currently circulating in human populations. Instead, the closest genetic relative to the strain came from samples taken from humans and mink in Michigan two years ago, tweeted Finlay Maguire, an assistant professor at Dalhousie University and one of the paper’s authors.

The researchers then compared the genetic makeup of coronavirus found in the deer to cases of the virus found in humans in the region.

The team found one resident who had a strikingly similar strain of the virus and who had been in contact with deer. While the authors said limited sample data made it difficult to fully understand the genetic relationship between the strains, the timing and location of the infection suggested a deer was the probable source.

Scientists aren’t sure how the deer contracted the virus initially, but further study of the variant circulating in the population suggested that its spike structure meant vaccine escape – the ability for virus to bypass vaccines – was unlikely.

“It’s reassuring that we found no evidence of further transmission, during a time when we were doing a lot of sampling and a lot of sequencing,” Samira Mubareka, a microbiologist and clinical scientist at Sunnybrook Health Sciences Centre, told CBC News. “If we continue to do this surveillance, we’ll get a much better sense of what the actual risk is.”

Experts have long worried that the virus could infect and then mutate within certain animals, known as reservoir species.

After reviewing the genetic sequence of the virus, Canada’s public health agency said there was no indication it had spread to humans and was probably an “isolated case”.

“Until we know more, people who hunt, trap or work closely with or handle wildlife should take precautions to prevent the potential spread of the virus,” the agency said on its website.

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