The USDA says the coronavirus is circulating widely in deer, and may be returning to people

There is no evidence that deer play a major role in the spread of the virus to humans, but transmission of the virus from humans to animals raises several public health concerns.

First, the animal reservoir could allow viral variants that have disappeared from humans to persist. Indeed, the new study confirms previous reports that some coronavirus variants, 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, which could lead to the emergence of new variants that can infect humans. If these variants are different enough from those previously circulating in humans, they can evade some of the immune system’s defences.

Animal and Plant Health Inspection Service researchers, in collaboration with government scientists and other academics, began looking for coronavirus in free-standing white-tailed deer in 2021, after studies indicated the animals were susceptible to the virus.

In that first year of monitoring work, scientists eventually collected more than 11,000 samples from deer in 26 states and Washington, D.C. Almost a third of the animals had antibodies to the coronavirus, indicating they had been previously exposed, and 12 percent were active. infected, APHIS said on 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 samples collected between November 2021 and April 2022. They found multiple copies of the virus in deer, including Alpha. Gamma, delta and omicron variables.

The scientists then compared viral samples isolated from deer with those from human patients and mapped the evolutionary relationships between them. They concluded that the virus was transmitted from humans to deer at least 109 times and that deer-to-deer transmission often followed.

The virus has also shown signs of adapting to deer, and researchers have identified several cases in North Carolina and Massachusetts in which humans were infected with these “deer-adapted” versions of the virus.

APHIS has expanded its monitoring to include additional cases and species.

Many questions remain, including specifically how people transmit the virus to deer, and what role animals might play in maintaining the virus in the wild.