First evidence of past SARS-CoV-2 exposure in U.S. marine mammals

What is it about?

Between 2020 and 2025, we investigated whether marine mammals in the United States had been exposed to SARS-CoV-2, the virus that causes COVID-19. We tested 1,808 nasal and oral swabs from 21 marine mammal species to look for active infections and 378 blood samples to determine whether animals had previously been exposed to the virus by detecting antibodies. We found no evidence of active SARS-CoV-2 infection, but we detected antibodies in harbor seals, California sea lions, and grey seals. These antibodies indicate that some animals had been exposed to the virus in the past, even though they were not actively infected when sampled. This study provides the first evidence of SARS-CoV-2 exposure in marine mammals in the United States and expands our understanding of how this virus has spread among wildlife.

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Photo by Simon Infanger on Unsplash

Photo by Simon Infanger on Unsplash

Why is it important?

SARS-CoV-2 has infected many animal species worldwide, raising concerns about wildlife becoming reservoirs for the virus. Understanding which species have been exposed is essential for protecting wildlife health and reducing the risk of future spillover between animals and humans. Although we found no active infections, the presence of antibodies demonstrates that exposure has occurred in free-ranging marine mammals. These findings emphasize the importance of continued surveillance as part of a One Health approach that recognizes the connections between human, animal, and environmental health.

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