Significance: SARS-CoV-2 is an emerging pathogen that has already had catastrophic consequences on the health and well-being of people worldwide. As a zoonotic virus, the implications for animal populations are largely unknown. This manuscript describes a pilot study in which domestic cats and dogs were assessed for their susceptibility to infection. While neither species developed clinical disease in this study, cats shed infectious virus for up to 5 d and infected naive cats via direct contact, while dogs do not appear to shed virus. Cats that were reinfected with SARS-CoV-2 mounted an effective immune response and did not become reinfected. These studies have important implications for animal health and suggest that cats may be a good model for vaccine development.

Significance: SARS-CoV-2 emerged because of viral spillover from animals to humans, and spillback to other animal species has been observed with accelerating frequency. Cross-species transmission generally results in the rapid adaptation of the virus to the new host, and repeated transmissions may hasten viral evolution and novel strain emergence. We report the surprisingly rapid selection of numerous SARS-CoV-2 variants in cell culture and following infection of nonhuman mammalian hosts, including dogs and cats. These molecular changes in SARS-CoV-2 provide insight into mechanisms of viral host adaptation, lay the groundwork for additional studies assessing dominant variant fitness and phenotype, and highlight the potential for human reinfection with new viral variants arising in species in close and frequent contact with humans.

Peridomestic Mammal Susceptibility to SARS-CoV-2

We report pilot studies to evaluate the susceptibility of common domestic livestock (cattle, sheep, goat, alpaca, rabbit, and horse) to intranasal infection with SARS-CoV-2. None of the infected animals shed infectious virus via nasal, oral, or fecal routes, although viral RNA was detected in several animals. Further, neutralizing antibody titers were low or non-existent one month following infection. These results suggest that domestic livestock are unlikely to contribute to SARS-CoV-2 epidemiology.

Powassan virus and its subtype, deer tick virus, are closely related tick-borne flaviviruses that circulate in North America. The incidence of human infection by these agents appears to have increased in recent years. To define exposure patterns among white-tailed deer, potentially useful sentinels that are frequently parasitized by ticks, we screened serum samples collected during 1979–2010 in Connecticut, Maine, and Vermont for neutralizing antibody by using a novel recombinant deer tick virus–West Nile virus chimeric virus. Evidence of exposure was detected in all three states. Overall our results demonstrate that seroprevalence is variable in time and space, suggesting that risk of exposure to Powassan virus is similarly variable.