COLUMBUS, Ohio — Deer may be the next carriers of COVID-19 who are able to infect humans, a new study warns. Scientists at The Ohio State University report that they have detected at least three variants of the virus in wild white-tailed deer throughout the state.
Researchers add that the animals may also be a potential “reservoir” for coronavirus, meaning COVID could survive within their bodies and evolve before jumping to humans.
“Based on evidence from other studies, we knew they were being exposed in the wild and that in the lab we could infect them and the virus could transmit from deer to deer. Here, we’re saying that in the wild, they are infected,” says senior author Professor Andrew Bowman in a university release.
“If they can maintain it, we have a new potential source of SARS-CoV-2 coming in to humans. That would mean that beyond tracking what’s in people, we’ll need to know what’s in the deer, too,” Bowman continues. “It could complicate future mitigation and control plans for COVID-19.”
1 in 3 deer may be carrying COVID-19
SARS-CoV-2 is the virus that causes COVID-19. Study authors identified the trio of mutations in over a third of 360 animals from six different locations. There was also evidence of virus transmission between the deer, suggesting deer may facilitate the emergence of more lethal variants.
Researchers confirmed their report of active COVID infections by growing viral isolates in lab experiments. This showed that the samples they collected of the SARS-CoV-2 virus were not just genetic traces, but full-blown infections.
The study follows previous research by the U.S. Department of Agriculture that also found COVID antibodies in wild deer. The team collected nasal swabs from the animals between January and March 2021, before the Delta variant became the world’s dominant strain. The study did not find cases of Delta in these deer.
Genomic sequencing showed the strains matched those in local patients with COVID in Ohio. Scientists are now testing more samples to check for new as well as older variants. Their continued presence would suggest the virus can “set up shop” and survive in wild deer for long periods of time.
Deer around crowded neighborhoods at high risk of infection
Prof. Bowman says the fact that wild deer can catch COVID-19 “leads toward the idea that we might actually have established a new maintenance host outside humans.”
At this point, researchers don’t know how these deer contracted COVID-19, if they can infect humans and other species, or how the virus behaves in their cells. So far, their analyses show the B.1.2 virus variant, dominant in Ohio in the early months of the year, spilled over multiple times into local deer populations.
“The working theory based on our sequences is that humans are giving it to deer, and apparently we gave it to them several times,” Bowman explains. “We have evidence of six different viral introductions into those deer populations. It’s not that a single population got it once and it spread.”
Study authors sampled deer sites between one and three times. Based on the findings, researchers estimate that the prevalence of COVID infection varied between 13.5 and 70 percent among the deer at nine sites. Moreover, they found the highest prevalence of virus cases in the four sites surrounding more densely populated neighborhoods.
New variants coming soon?
Prof. Bowman believes if deer function as a viral reservoir for COVID, it would result in one of two likely outcomes. First, COVID would mutate in deer, leading to the transmission of new strains to other species, including humans. Second, the virus could survive in deer unmutated while it simultaneously continues to evolve in humans.
At some point, when we don’t have immunity to the strains infecting deer, those variants would come spilling back into people. As for how COVID got into deer in the first place, study authors speculate that white-tailed deer were infected through contaminated water or another environmental pathway.
Previous studies have found that infections among cats and dogs have a link to human contact, contact with wildlife under human care, and encounters with free-ranging wildlife.
Estimates put the white-tailed deer population in Ohio alone at around 600,000 and there are around 30 million deer throughout the U.S.
“No spillback to humans was observed, but these findings demonstrate that SARS-CoV-2 viruses have the capacity to transmit in US wildlife, potentially opening new pathways for evolution,” the team writes in the journal Nature.
South West News Service writer Mark Waghorn contributed to this report.