H5N1 Bird Flu Detected in California Elephant Seals

Researchers confirm first cases of deadly virus in marine mammals along the state's coast.

Published on Feb. 25, 2026

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Researchers at UC Davis and UC Santa Cruz have confirmed the presence of the H5N1 bird flu virus in seven weaned elephant seal pups at Año Nuevo State Park in California. This marks the first time the deadly virus has been detected in the state's marine mammal population. The confirmation came from testing conducted at the U.S. Department of Agriculture's laboratory in Ames, Iowa.

Why it matters

The H5N1 bird flu virus has devastated wild, commercial, and domestic animal populations across the globe in recent years. Its spread to California's elephant seal colonies raises concerns about the potential impact on the state's marine ecosystems and the risk of further transmission to other species.

The details

While the exact number of affected animals has not been provided, the UC Davis press release noted that at least some elephant seals have already succumbed to the virus. Researchers say the rapid detection of the outbreak is due to coordinated surveillance teams that have been on high alert for this disease.

  • The confirmation of H5N1 in the elephant seals came on February 25, 2026.

The players

UC Davis

A public research university located in Davis, California, known for its programs in veterinary medicine and wildlife research.

UC Santa Cruz

A public research university located in Santa Cruz, California, with a focus on marine and environmental sciences.

U.S. Department of Agriculture

The federal agency responsible for developing and executing policies related to agriculture, food, natural resources, and related issues.

Christine Johnson

Professor and director of the Institute for Pandemic Insights at the UC Davis Weill School of Veterinary Medicine.

Año Nuevo State Park

A California state park located on the coast of San Mateo County, known for its large elephant seal colony.

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What they’re saying

“This is exceptionally rapid detection of an outbreak in free-ranging marine mammals. We have most likely identified the very first cases here because of coordinated teams that have been on high alert with active surveillance for this disease for some time.”

— Christine Johnson, Professor and director of the Institute for Pandemic Insights (UC Davis)

What’s next

Researchers and wildlife officials will continue to monitor the elephant seal population at Año Nuevo State Park and surrounding areas for any further spread of the H5N1 virus. Efforts to understand the transmission and impact of the virus on marine mammals will be a priority.

The takeaway

The detection of H5N1 bird flu in California's elephant seal population underscores the need for vigilant disease surveillance and preparedness, especially in vulnerable wildlife populations. This outbreak serves as a reminder of the potential for zoonotic diseases to cross over from birds to other species, with potentially far-reaching consequences for ecosystems and public health.