UPDATE:
05/12/2026: (From the Institute for Pandemic Insights at University of California, Davis) The HPAI H5N1 outbreak in marine mammals in California, which occurred between February 12 and March 24, 2026, is now officially over, with no new positive cases found in tested marine mammals for over 30 days. The outbreak resulted in 64 positive marine mammal cases out of 233 tested animals (27% overall positivity). Positive cases included 57 elephant seals, 6 California sea lions, and 1 southern sea otter. The majority of cases in marine mammals (57) were concentrated in San Mateo County, with additional positive cases in Santa Cruz, Monterey, and San Luis Obispo counties. Preliminary analyses have shown that the sequences from the outbreak cluster tightly as the HPAI H5N1 A3 genotype.
Scientists are returning to normal research efforts, including routine surveys to look for sick elephant seals at Año Nuevo Reserve. Post-outbreak investigations of stranded marine mammals throughout California include screening of animals that could be suspect for HPAI H5N1 infection, based on all that we have learned during this outbreak. We plan to increase surveillance activities in marine mammals during the next bird migration in the fall of 2026.
We are very grateful to the partners listed below that supported the outbreak investigations, the many federal, state, and local agencies that oversaw aspects of this response, and the frontline responders that constitute the NOAA Fisheries West Coast Marine Mammal Stranding Network.
03/26/2026: Scientists have confirmed a case of HPAI H5N1 in a California sea lion in San Luis Obispo County, California. The young (1-2 year old) dead sea lion was sampled by a researcher from Central California Marine Animal Response Team (CCMART) on March 16, and samples were sent to UC Davis and the USDA’s NVSL lab where presence of the virus was confirmed on March 25.
This is the first report of HPAI in a marine mammal from San Luis Obispo County which is south of the main outbreak response area in San Mateo County. Juvenile sea lions are known to forage along the central California coast traveling as far south as the primary sea lion breeding colonies on the Channel Islands. Researchers are continuing to monitor marine mammal populations all along the coast.
Elephant seals recently sampled at the Piedras Blancas rookery have tested negative for the H5N1 virus. The Elephant Seal Viewing Area and Visitor Center remain open to the public. At the same time, we all remain on alert for any signs of disease at the Piedras Blancas Elephant Seal Rookery.
Since 2024, scientists have been monitoring seabirds and elephant seals up and down the California coast, and the outbreak at the Año Nuevo elephant seal rookery near Santa Cruz was the first detection in northern elephant seals to date.
The following page: from the University of California, Davis, provides more information about the current outbreak: https://pandemicinsights.ucdavis.edu/h5-marine-outbreak
Public guidance remains the same:
-Stay 150 yards away from all marine mammals and seabirds;
-Keep children and pets away from sick, injured or dead wildlife;
-Do not approach, touch or attempt to assist marine mammals or seabirds.
-Call NOAA West Coast Marine Mammal Stranding Hotline 866-767-6114 for sick, injured or dead marine mammals.
The Elephant Seal Visitor Center in San Simeon (250 San Simeon Ave, Suite 3B, San Simeon, CA) is open daily from 10am to 4pm and offers a live webcam view of the rookery, along with knowledgeable staff who can tell you about e-seals and answer questions. It is a good place to begin or end your elephant seal adventure.