Dr. Scott Weese wears a lab coat and smiles
Dr. Scott Weese

New research by a team of Canadian scientists suggesting deer in Ontario may be able to transmit the virus that causes COVID-19 to humans is “concerning,” says a University of Guelph veterinary internal medicine researcher.

Dr. Scott Weese, chief of infection control at the Ontario Veterinary College (OVC), has studied the spread of the SARS-CoV-2 virus from humans to animals throughout the pandemic.

He said the new, unpublished research posted online Friday raises many questions. (The study has not been peer-reviewed and Weese was not involved in it.)

The research is based on a small number of viral samples, “but the story is pretty compelling and concerning,” Weese wrote on his blog, Worms and Germs.

The scientists discovered a cluster of SARS-CoV-2 in wild deer with many new mutations, suggesting the virus has been spreading in deer for much longer than previously thought, Weese said.

Need to continue to study spread of SARS-CoV-2 in animals

The finding that an Ontario man with COVID-19 had a strain of the virus with most of the same mutations in this deer cluster is also of concern, said Weese. It may mean the deer transmitted the virus to the man, though it may have been the other way around.

“This gets us back to the ‘chicken vs egg’ discussion. Did this person get infected from deer, or were they a source of infection for deer?” Weese said.

He added that reduced COVID-19 testing during this winter’s Omicron wave makes it difficult to know whether other humans have also been infected with strains similar to that seen in the deer cluster.

Speaking to CNN Health, Weese said the study may be indication of a “spillback” event in which the virus has changed in an animal population.

“It’s actually a pretty significant study, I think, because we’re seeing potential evolution of the virus in an animal reservoir,” he said.

“…It went somewhere and changed over the course of months to a year, and it looks like most likely that was within an animal.

Weese also noted to CNN that deer are the ideal hosts for SARS-CoV-2: they are highly susceptible to infection, they don’t get very sick and they nest in groups, making it easy for the virus to spread.

The paper raises many more questions, such as whether deer have become a reservoir for COVID-19 and whether the virus is also present and mutating in other wildlife.

“Much of the story here is quite speculative, but it’s why we’ve been talking about the need to study SARS-CoV-2 in animals from the start of the pandemic.

“Those pleas were largely ignored for a long time, so now we’re playing catch-up.”

Weese is a professor in the Department of Pathobiology and the director of the Centre for Public Health and Zoonoses.

He is available for interviews.


Dr. Scott Weese