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 the transmission of the virus from humans to animals has raised some public health concerns.
First, the animal reservoir may allow viral variants lost in the human population to persist. In fact, the new study confirms earlier reports that some coronavirus variants, including Alpha and Gamma, continue to circulate in deer even after they have become rare in humans.
New animal hosts also give the virus new opportunities to mutate and evolve, potentially giving rise to new variants that can infect humans. If these variants are different enough from those that have previously circulated in humans, they may evade some of the immune system’s defenses.
Background: Scientists find signs of widespread infection in deer.
Researchers at the Animal and Plant Health Inspection Service, in collaboration with other government and academic scientists, began looking for the coronavirus in free-ranging white-tailed deer in 2021, after studies suggested the animals were susceptible to viruses.
In the first year of surveillance work, scientists ultimately collected more than 11,000 samples from deer in 26 states and Washington, D.C. Nearly one-third of the animals had antibodies to the coronavirus, suggesting they were previously exposed, and 12 percent are actively infected, APHIS said Tuesday.
For the new Nature Communications paper, scientists from APHIS, the Centers for Disease Control and Prevention and the University of Missouri sequenced nearly 400 of the samples collected between November 2021 and April 2022. They found of multiple versions of the virus in deer, including Alpha, Gamma, Delta and Omicron variants.
The scientists then compared viral samples isolated from deer to those from human patients and mapped the evolutionary relationships between them. They concluded that the virus had moved from humans to deer at least 109 times and was often followed by deer-to-deer transmission.
The virus has also shown signs of adapting to deer, and researchers have identified several cases in North Carolina and Massachusetts where humans have been infected with “deer-adapted” versions of this virus.
What’s Next: Monitoring will continue.
APHIS has expanded its surveillance to additional states and species.
Many questions remain, including exactly how humans transmit the virus to deer, and the role the animals may play in maintaining the virus in the wild.