Why it matters: Deer can be a source of new variants.
There is no evidence that deer play a major role in the spread of the virus to humans, but human-to-animal transmission of the virus raises several public health concerns.
First, an animal reservoir could allow viral variants that have disappeared from human populations to persist. Indeed, the new study confirms previous reports that some variants of the coronavirus, including Alpha and Gamma, continued to circulate in deer even after they became rare in humans.
New animal hosts also give the virus new opportunities to mutate and evolve, potentially creating new variants that can infect humans. If these variants differ enough from those previously circulating in humans, they could evade some of the immune system’s defences.
Background: Scientists have found signs of widespread infection in deer.
Researchers from the Animal and Plant Health Inspectorate, in collaboration with other government and academic scientists, started looking for the corona virus in free-roaming white-tailed deer in 2021, after research showed that the animals were susceptible to the virus.
In that first year of surveillance work, the scientists eventually collected more than 11,000 samples from deer in 26 states and Washington, DC. Nearly a third of the animals had antibodies to the coronavirus, suggesting they had been previously exposed, and 12 percent were actively infected, APHIS said Tuesday.
For the new paper from Nature Communications, scientists from APHIS, the Centers from Disease Control and Prevention and the University of Missouri sequenced nearly 400 of the samples collected between November 2021 and April 2022. They found multiple versions of the virus in deer, including the Alpha, Gamma, Delta, and Omicron variants.
Next, the scientists compared the viral samples isolated from deer with those from human patients and charted the evolutionary relationships between them. They concluded that the virus passed from human to deer at least 109 times, and that deer-to-deer transmission often followed.
The virus also showed signs of adapting to deer, and the researchers identified several cases in North Carolina and Massachusetts in which people were infected with these “deer-adapted” versions of the virus.
What’s Next: Surveillance continues.
APHIS has expanded its surveillance to other states and species.
Many questions remain, including how exactly humans transmit the virus to deer and what role the animals might play in helping to maintain the virus in the wild.
