If white-tailed deer become a reservoir for the virus, the pathogen could mutate and spread to other animals or back to us. Adaptation in animals is one route by which new variants are likely to emerge.

“This is a top concern right now for the United States,” said Dr. Casey Barton Behravesh, who directs the One Health Office — which focuses on connections between human, animal and environmental health — at the Centers for Disease Control and Prevention.

“If deer were to become established as a North American wildlife reservoir, and we do think they’re at risk of that, there are real concerns for the health of other wildlife species, livestock, pets and even people,” she added.