An Omicron-like version of the virus that causes COVID-19 - one that appears to be highly different from circulating strains and clings to a long branch of the virus' family tree - has been discovered in a white-tailed population. According to a new study, deer in Ontario, Canada.
The same strain has also been found in a person from the same area who had confirmed contact with deer, but there is no evidence of continued transmission from deer to humans, and it is unlikely to pose an immediate threat to humans.
Researchers who first characterized the Ontario WTD clade say it is difficult to determine how this lineage evolved because it appears to have gone unnoticed in the background of the pandemic for nearly a year and without sampling. 's gone. They speculate that it spread from humans to deer and then to at least one human.
The new branch of the SARS-CoV-2 family tree has about 79 gene changes that differentiate it from the original strain of the virus that was first identified in Wuhan, China. About half of those changes - 37 - have been observed in animals, but 23 of them have never been identified in deer before.
"This is actually a very important study, I think, because we are looking at the potential evolution of the virus in an animal reservoir," said Professor J. Scott Weiss, who specializes in the study of infections. Jump between animals and people.
Weiss says that before, we could see the SARS-CoV-2 virus passing between people and animals, but then stop. There was no indication that it was persisting and changing in animal populations following these spillover or spillback events.
The closest viral relatives of the new clade, however, are 10 to 12 months earlier to humans and mink in Michigan on the border from Ontario.
"It went somewhere and changed over the course of months to a year, and it seems most likely it was within an animal. We just don't know which species or where," Weiss says, who reviewed the study but was not involved in the research.
The study was posted to the preprint server BioRxiv prior to peer review.
Signs of a new animal reservoir
In many ways, deer are ideal hosts for SARS-CoV-2, Weese says. They are susceptible to infection, but they don't get very sick, and they tend to nest in groups, which makes it easier for the virus to spread.
This new breed was discovered during the hunting season. The hunters brought the deer they had killed to scientists, who swabbed and tested them.
Researchers say there is no evidence that this strain resulted in deer-to-human or human-to-human transmission. However, the hunting season in the region has come to an end, and the Omicron wave has advanced, complicating further monitoring.
Preliminary laboratory experiments suggest that the new strain is easily knocked down by antibodies created in response to vaccination, making this version of the virus unlikely to pose an immediate threat.
The problem is what could happen in the future.
"I think most people were thinking -- and it's true -- that humans are driving the epidemic," said study author Bradley Pickering, chief of specialty pathogens at Canada's National Center for Foreign Animal Disease. "So now, it looks like it's rolling into the wildlife."
If it remains in deer in North America, it may continue to circulate and mutate.
"You have that risk, that it's always there and that -- at any point -- it could come back for people," he said.
Pickering says researchers are going to try to restart their monitoring of deer populations to continue monitoring the evolution of the virus.
If deer have become a true animal reservoir, it is a difficult problem to solve, and it signals a new phase in the epidemic, Weiss says.
"We need to go beyond a human-centered approach. Person means individual; it doesn't mean people," Weiss said. "It doesn't matter if it's spreading to 100 million people in a fully vaccinated area of the world or if it's circulating in 10 million deer in North America. It's circulating, and as such the virus spreads and replicates." That's how mutation happens."
Another way to avoid virus
When SARS-CoV-2 mutates into a population of farmed animals such as minks, or hamsters, sold at pet stores in Hong Kong, they are often killed to stop the spread of the virus.
This is not possible when the virus is in a population of wild animals.
Animals have vaccines, but veterinarians use them for the same reasons they give them to humans, to prevent disease and to keep the animal -- a tiger in a zoo, for example -- from becoming seriously ill. or by death.
"Vaccines aren't highly effective at preventing transmission," Weese said. "We would have to have an animal vaccine that's better than a human vaccine, and the animal vaccines are an older technology, so that would be a pretty high bar to set."