White-Tailed Deer Harbor SARS-CoV-2 Variants No Longer Infecting Humans, Study Finds

White-tailed deer may act as reservoirs for SARS-CoV-2 variants that have gone extinct in human populations, raising concerns about the possibility of spillback of animal-adapted viral variants to humans, according to a study in this week's Proceedings of the National Academy of Sciences. Genomic studies point to a broad host range for SARS-CoV-2 and research has shown that white-tailed deer can be infected and pass the virus to one another. Given the large numbers of these animals throughout the US and their potential as reservoirs of SARS-CoV-2, a group led by Cornell University researchers performed a cross-sectional study to assess the prevalence, genetic diversity, and evolution of SARS-CoV-2 in white-tailed deer in New York State. They analyzed retropharyngeal lymph node samples from around 5,500 animals harvested during the 2020 and 2021 hunting seasons, finding that many of the deer were infected with three major SARS-CoV-2 variants of concern long after they had last been detected in humans. Additionally, the viral sequences found in the deer were highly divergent from the sequences in humans, suggesting that they had rapidly adapted to the animals. The findings indicate that white-tailed deer may harbor SARS-CoV-2 variants of concern no longer circulating among humans. As such, surveillance programs monitoring SARS-CoV-2 dynamics in white-tailed deer, as well as measures to reduce viral transmission between humans and animals, are needed, the study's authors write.