The COVID-19 pandemic is not over yet. The world has continued to record new infections, detect new coronavirus variants, and extract more information about the virus and the disease it causes. And now, new research may have found evidence that the novel coronavirus has made a three-point jump: from humans to deer, then back to humans!
During the first lockdown, when the world was still bearing the full brunt of the COVID-19 pandemic, a team of researchers from the University of Toronto began searching wild animals for traces of the SARS-CoV-2 virus in the origin of COVID. This was after the fallout of humans on animals (especially those in the zoo) became apparent and widely reported.
The team’s initial efforts, focused on 20 different species (including raccoons and bats), yielded no results. But in 2021, when reports of deer infection surfaced in the United States, researchers restarted testing on white-tailed deer commonly found in Ontario and Quebec in Canada.
Not only did the researchers detect traces of COVID infection in these deer, but they were also able to isolate live virus from two out of three nasal swabs that tested positive for COVID-19.
First Evidence of Deer-to-Human Coronavirus Transmission
After further analysis, the researchers identified a highly divergent lineage of SARS-CoV-2 in white-tailed deer. Named B.1.641, this line is one of the most divergent SARS-CoV-2 lines detected to date, with 76 mutations. Such a divergence from the ancestral strain indicates that it had been circulating and evolving in the deer population undetected for months!
Surprisingly, one of the samples taken from infected people in Ontario around the same time as the deer study had a variant quite similar to the “deer virus strain”. This indicates that the virus first infected the deer population and then returned to humans!
Elaborating on the potential circumstances under which this spillover may have taken place, study co-author Samira Mubareka explained, “There are many human-deer interfaces, including public interactions with wild deer and deer. captives for breeding, exhibition or hunting. For many communities, deer are important from both a food security and cultural perspective.
The good news is that, unlike Omicron, this variant cannot bypass the immune system of vaccinated or previously infected people. Despite its spike protein mutations, the virus was able to be neutralized using blood samples from people who had recovered from COVID-19 or received two or three doses of the vaccine.
Follow-up work is underway to understand how this deer-to-human spillover actually happened. While pathogens continue to move back and forth between different hosts to complete their life cycle, their nature changes when these disease carriers are introduced into a new host. This creates space for mutations that can not only re-infect humans, but also evolve in ways that make them difficult to detect and treat.
Meanwhile, Canadian health authorities have issued advisories on how to safely interact with deer and reduce the risk of transmission.
Overall, this study highlights the importance of wildlife monitoring, which can help us better understand the complexities and risks associated with future outbreaks and structure our response to the pandemic accordingly.
The study was published in the journal Natural microbiology and accessible here.
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