In a world first, preliminary research suggests deer may be able to transmit the COVID-19 virus to humans, following analysis by a team of Canadian scientists monitoring the spread of SARS-CoV-2 in animals .
So far, researchers have only found evidence that humans transmit the virus to deer and that deer transmit it to other deer.
New evidence suggesting the virus may be able to spread from deer to humans is an important development as scientists closely monitor whether wild animals could become a source of new variants and act as a reservoir for SARS-CoV- 2.
Yet humans remain the main source of the virus and its spread around the world.
The new research paper published Friday on bioRxiv, an online archive and distribution service for unpublished preprints in the life sciences, has not been peer-reviewed.
The findings stem from the work of a team of scientists who collaborated to analyze samples taken from hundreds of deer killed by hunters in the fall of 2021 in southwestern Ontario.
In their analysis, the scientists discovered a highly divergent lineage of SARS-CoV-2 – which essentially means a group of viruses with many mutations.
Around the same time, a genetically similar version of the virus was identified in a person from the same region of Ontario who had recently come into contact with deer.
These were all sampled in southwestern and eastern Ontario with the help of hunters. We found 17/298 deer sampled positive for SARS-CoV-2 (all from southwestern Ontario) via nasal swabs and lymph node samples (checking carefully for contamination) /2 pic.twitter.com/XNVsByaSsC
Finlay Maguire, who collaborated on the research and helped analyze the genetic sequencing, pointed to the fact that no other cases were found in humans.
“This particular case, while raising a red flag, does not appear to be extremely alarming.”
He said their findings come down to strong circumstantial evidence.
“While we have not seen [transmission from deer to human] happen directly, we sampled from the human case around the same time we sampled from the deer, and we sampled around the same location,” Maguire said. “There is also a plausible link by which this could have occurred, in that the individual involved is known to have had considerable contact with deer.”
The research underscores the need for better surveillance of the COVID-19 virus — not just in humans, but also in animals, plants and the wider environment, said Maguire, an assistant professor at Dalhousie University and Head of Pathogen Bioinformatics at Sunnybrook Health Sciences Center in Toronto.
Need better monitoring
How the deer caught the virus in the first place is unclear, which is one reason Maguire and others say greater surveillance is needed.
It could have been transmitted by humans directly, or through sewage or an intermediate animal host, such as mink.
Together this suggests a virus that diverged unobserved over 1-2 years (likely in association with deer). Given possible deer-to-human transmission, it is important that we assess possible reservoirs and adopt one-health approaches in our surveillance of SARS-CoV-2. /end pic.twitter.com/8mILYJtiMu
Samira Mubareka, an infectious disease physician and virologist at Sunnybrook Health Sciences Center in Toronto, said the version of the virus they found was different from the one currently circulating.
“It’s not even closely related to Delta or Omicron. Its most recent parent was in 2020.”
Mubareka, one of the authors of the research paper, said this means that it took time for the divergent lineage to mutate and emerge.
“It’s reassuring that we found no evidence of further transmission, at a time when we were doing a lot of sampling and a lot of sequencing,” said Mubareka, a microbiologist and clinician-scientist at Sunnybrook Health Sciences Center.
“If we continue to do this monitoring, we will have a much better idea of the real risk.”
Previously, the only other known cases of animal-to-human transmission were in farmed mink. There is also preliminary research in Hong Kong suggesting the virus could spread from hamsters to humans.
Hunters must be careful
For most people, the risk of catching the virus from a human is much higher than catching it from a deer.
The Public Health Agency of Canada (PHAC) has said there is no evidence that animals play a significant role in the current spread of COVID-19 and that animal-to-human transmission is rare, but the agency warns hunters to be cautious.
Hunters and people handling wild deer are advised to wash their hands regularly, wear gloves, goggles and a properly fitted mask when there is a possibility of exposure to respiratory tissues and fluids, especially inside.
Coronaviruses are killed by normal cooking temperatures and there is no evidence that cooked venison can spread the COVID-19 virus.
PHAC said scientists at the National Microbiology Laboratory have reviewed the findings of the research paper and confirmed that the genetic similarities suggest the possibility of deer-to-human transmission in this case.
“Based on the information available to date, there is no evidence of additional human infections with this unique sequence, as this single human case has been identified,” a PHAC statement read.
“Routine genomic surveillance will continue to monitor positive PCRs [polymerase chain reaction] test results for unusual variations of the virus in Canada, including this one. »