SARS-CoV-2 Delta variant re-emerges in US farmed mink and free-ranging white-tailed deer in 2022-2023 (opens in a new tab)

American mink (Neogale vison) are susceptible to SARS-CoV-2, but little is known about virus circulation in mink since 2021. Here, in the first active surveillance study of SARS-CoV-2 in apparently healthy farmed mink in the United States, we find a ~0.9% (760/85,656) RT-PCR positivity rate among nasal swabs collected in 18 farms across six states during 2022-2023. Phylogenetic analysis of 293 viral genome sequences shows that human-adapted SARS-CoV-2 variants (e.g., Omicron) repeatedly spill over into mink. Surprisingly, the detection of a Delta lineage virus (AY.39) on a mink farm four months after its last detection in humans within the same state suggests prolonged unsampled transmission. The spread of mink-adapted AY.39 viruses from a mink farm to neighboring free-ranging white-tailed deer represents a rare instance of SARS-CoV-2 transmission between livestock and wildlife. These findings demonstrate the value of active surveillance for identifying subclinical infections and interspecies transmission between humans, mink, and wildlife.