Elephant Seals at California’s Año Nuevo Test Positive for H5N1 Bird Flu

Confirmed cases of highly pathogenic avian influenza H5N1 have been detected in northern elephant seals at Año Nuevo State Park in California, marking the first such occurrence in the state’s marine mammals.

Seven weaned seal pups tested positive for the virus, with laboratory confirmation provided by the U.S. Department of Agriculture’s National Veterinary Services Laboratory. Researchers observed abnormal respiratory and neurological symptoms, such as weakness and tremors, in affected seals on February 19 and 20, 2026.

Since the initial observations, approximately 30 elephant seals, mostly weaned pups, have died at the site. The elephant seal colony at Año Nuevo State Park typically includes about 5,000 animals during the winter breeding season, with an estimated 1,350 present when the outbreak began.

California State Parks responded by temporarily closing public access to seal viewing areas and canceling guided tours for the rest of the season. This action was taken to limit human and animal contact with the affected seals and to support ongoing monitoring efforts.

What the numbers show

• Seven seal pups tested positive for H5N1 avian influenza
• About 30 seal deaths reported since February 19, 2026
• Approximately 1,350 seals were present at the colony during the outbreak

Researchers from UC Santa Cruz and UC Davis have increased disease surveillance at Año Nuevo in recent years, focusing on the potential spread of avian influenza among marine mammals. Scientists are also collaborating with NOAA Fisheries, the California Department of Fish and Wildlife, and the West Coast Marine Mammal Stranding Network to monitor the situation along the coast.

This incident represents the first confirmed detection of HPAI H5N1 in northern elephant seals and in any marine mammal species in California. Surveillance and testing efforts have been expanded in response to the outbreak to better understand the impact on the seal population.

According to the University of California, Davis, the risk of infection to the general public is considered very low. However, authorities advise people and pets to avoid contact with both live and dead seals to minimize any potential risk.

* This article is based on publicly available information at the time of writing.