News that the virus that causes COVID-19 has been found in wild deer in Canada is concerning, particularly if the virus spreads to other wild species, says a University of Guelph infection control expert.

SARS-CoV-2 was found in three white-tailed deer after samples were taken in early November in the Eastern Townships region in Quebec.

Dr. Scott Weese, a professor and chief of infection control at the Ontario Veterinary College (OVC), said it is not surprising that the virus was found in Canadian deer. Earlier this year, deer were put on a large and growing list of species deemed susceptible to the virus based on research done in the U.S.

Prof. Scott Weese in his lab
Dr. Scott Weese

However, now that we know it is present in Canada, we need to determine whether the deer are spreading the virus to other deer and to other species, he added.

“We really don’t want SARS-CoV-2 to become established in wildlife, as that creates the potential for a reservoir of infection for people and other species and the potential emergence of new mutants, or variants of concern, that could cause issues if they spread back into people.”

One key component required for an animal reservoir is a large population of susceptible individuals to allow the continued circulation of the virus, he said.

“There are in fact large, relatively mobile populations of deer across wide ranges of North America.”

In the U.S., researchers have found high rates of the virus in the blood of deer. This could mean the virus gets into the population, spreads quickly to other deer and then burns out and disappears, he said.

“However, it could mean that the virus circulates through the population as it continues to find new susceptible deer at a slower pace. This is the big question that needs to be answered.”

Whether or not the presence of the virus in deer will lead to more variants depends on the amount of the virus circulating in the population, he said.

“Mutations occur during virus replication. The more transmission, the more replication and the great the risk of variants emerging.”

Beyond investigating the spread among deer, we need to determine if deer are spreading it to other species, he said.

If the virus is being spread among different species, it will be challenging to control, he added.

“Controlling the spread within the human population is easier than trying to control it among a number of species.”

We also need to investigate how the virus spread to deer in the first place. While it is still a large unknown, one possibility is an intermediate host that carries the virus from humans to deer, he said.

To help prevent the spread of the virus from deer to humans, Weese said, hunters should take extra precautions, including wearing a mask when handling deer carcasses.

To better understand how this virus is spreading among wildlife, we need more surveillance to determine whether sustained transmission occurs in deer populations and whether that transmission is leading to the emergence of significant variants, said Weese.

“Hunting history and deer contact history should be considered when investigating new cases of COVID-19 in people, especially when there’s no other clear source.”

Weese, a veterinary internal medicine specialist, has studied the SARS-CoV-2 virus and the spread from humans to animals during the pandemic.

He is available for interviews.


Dr. Scott Weese