A group of young seals lounging together on a sandy beach. — A group of healthy weaned elephant seal pups on the beach at Año Nuevo State Park. The variation in fur color is a normal process of molting each year. Photo by Frans Lanting for the Beltran Lab / UC Santa Cruz under NMFS Permit 28742.

First Cases of Highly Pathogenic Avian Influenza in Northern Elephant Seals Confirmed in California

Cases at Año Nuevo State Park Mark State’s First Detection of the Disease in a Marine Mammal

by UC Davis News and Media Relations
February 25, 2026

Seven weaned elephant seal pups in California’s Año Nuevo State Park tested positive for highly pathogenic avian influenza (HPAI) H5N1, the U.S. Department of Agriculture’s National Veterinary Services Laboratory confirmed Tuesday evening.

The outbreak marks the first cases of HPAI H5N1 in marine mammals in California and the first detection in northern elephant seals. The disease decimated populations of a related species, southern elephant seals, in Argentina in 2023.

First Cases of Highly Pathogenic Avian Influenza in Northern Elephant Seals Confirmed in California

Cases at Año Nuevo State Park Mark State’s First Detection of the Disease in a Marine Mammal

Read more about this outbreak and how the Institute for Pandemic Insights is collaborating with stakeholders across the country to support rapid response.