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Bird Flu Hits Bay Area Seal Colony, Alarming Researchers
Seven elephant seal pups test positive for highly pathogenic H5N1 strain in first confirmed cases in California marine mammals.
Published on Feb. 25, 2026
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Researchers at UC Santa Cruz have confirmed that seven elephant seal pups at Año Nuevo State Park in San Mateo County have tested positive for the highly pathogenic H5N1 strain of bird flu, marking the first known cases of the virus in marine mammals in California. The seals have exhibited respiratory and neurological symptoms, and an unknown number have died, though officials say the overall number of cases is 'small.' State parks have closed public access to the area as they investigate the outbreak.
Why it matters
The detection of H5N1 in the Bay Area seal colony is concerning, as the virus has previously caused devastating impacts on seal populations in other parts of the world. While the risk of human transmission is considered low, officials are urging the public to avoid contact with both live and dead seals to prevent potential spread.
The details
Researchers at UC Santa Cruz first noticed the seals exhibiting unusual symptoms, including weakness and tremors, late last week. Seven weaned elephant seal pups subsequently tested positive for the H5N1 virus. An unknown number of seals have died, but California State Parks believes the overall number of cases is 'small.' State parks have closed public access to viewing areas until Sunday as multiple agencies investigate the outbreak.
- Late last week, researchers at UC Santa Cruz noticed the seals exhibiting unusual symptoms.
- Seven weaned elephant seal pups have since tested positive for the H5N1 virus.
The players
UC Santa Cruz
A university whose researchers lead the northern elephant seal research program at Año Nuevo State Park.
Roxanne Beltran
The lead researcher of UC Santa Cruz's northern elephant seal research program at Año Nuevo.
California State Parks
The state agency that manages Año Nuevo State Park and has closed public access to the area as the outbreak is investigated.
What they’re saying
“Given the catastrophic impacts observed in related species, we were concerned about the possibility of the virus infecting northern elephant seals for the first time, so we ramped up monitoring to detect any early signs of abnormalities.”
— Roxanne Beltran, Lead researcher, UC Santa Cruz northern elephant seal research program (San Francisco Chronicle)
“We are cautiously optimistic, as most of the adult females had already departed the beach for their routine migrations before the outbreak began.”
— Roxanne Beltran, Lead researcher, UC Santa Cruz northern elephant seal research program (San Francisco Chronicle)
What’s next
State parks officials have closed public access to viewing areas until Sunday as multiple agencies investigate the outbreak. Most seals on the beach appear healthy, officials said.
The takeaway
The detection of the highly pathogenic H5N1 bird flu strain in the Bay Area seal colony is a concerning development, as the virus has previously caused devastating impacts on seal populations in other parts of the world. While the risk of human transmission is considered low, officials are urging the public to avoid contact with both live and dead seals to prevent potential spread.
