Strategies Proposed to Shield Seals, Sea Lions From Bird Flu

UC Davis study examines impact of H5N1 avian influenza on pinnipeds and offers recommendations for monitoring, risk characterization, and building resilience.

Mar. 20, 2026 at 3:08am

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A study from the University of California, Davis, examines the widespread impact of the H5N1 highly pathogenic avian influenza virus on pinnipeds, including seals and sea lions, worldwide. The paper offers key recommendations for monitoring, characterizing risk, and building resilience in affected species, as well as ways to help prevent the virus from reaching currently unaffected but vulnerable pinniped species.

Why it matters

Pinnipeds have been hit unusually hard by the H5N1 avian influenza virus, with outbreaks killing tens of thousands of seals and sea lions in South America. The study highlights the urgent need for coordinated efforts to monitor wildlife health, detect outbreaks early, and address the root causes of these emerging infectious diseases that threaten vulnerable marine species.

The details

The paper, published in Philosophical Transactions B, states that throughout Peru, Chile, Brazil, Uruguay and Argentina, highly pathogenic avian flu outbreaks have killed at least 36,000 South American sea lions, 17,400 southern elephant seals, and 1,000 South American fur seals. The authors call this an "unprecedented conservation risk" as the virus continues to evolve and spread. The study also chronicles a massive 2023 outbreak of HPAI H5N1 in southern elephant seals in Argentina, which the authors describe as the "canary in the coal mine" alerting researchers to the broader issue affecting pinnipeds worldwide.

  • In late February 2026, northern elephant seals in California marked the first cases of HPAI H5N1 in a marine mammal in the state.
  • At the end of 2025, in response to a growing number of H5N1 cases in Bay Area seabirds, the UC Davis team increased surveying efforts at the Año Nuevo Natural Reserve.

The players

Christine Johnson

Director of the Institute for Pandemic Insights at the UC Davis Weill School of Veterinary Medicine.

Marcela Uhart

A veterinarian with the UC Davis Karen C. Drayer Wildlife Health Center and its Latin America Program.

Elizabeth Ashley

A graduate student researcher pursuing a dual degree in veterinary medicine and epidemiology at UC Davis.

Ralph Vanstreels

A co-first author from the UC Davis Weill School of Veterinary Medicine.

Año Nuevo Natural Reserve

A reserve in California that collaborated with UC Davis and UC Santa Cruz on monitoring northern elephant seals.

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What they’re saying

“There is a huge, unprecedented conservation risk. Influenza is constantly changing, and that is a big problem now that it's widely circulating in birds and marine mammals.”

— Christine Johnson, Director of the Institute for Pandemic Insights at the UC Davis Weill School of Veterinary Medicine

“Southern elephant seals were the canary in the coal mine alerting us to a bigger issue of pinnipeds throughout the entire world. We can do something better to be prepared the next time before it spreads to other species.”

— Marcela Uhart, Veterinarian with the UC Davis Karen C. Drayer Wildlife Health Center and its Latin America Program

“H5 avian influenza viruses are an emergent threat to seal and sea lion populations already facing numerous conservation pressures. Understanding how this virus spreads in coastal ecosystems is critical for protecting vulnerable marine wildlife.”

— Elizabeth Ashley, Graduate student researcher at UC Davis

What’s next

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The takeaway

This study highlights the urgent need for coordinated, proactive efforts to monitor wildlife health, detect avian influenza outbreaks early, and address the root causes of these emerging infectious diseases that threaten vulnerable marine species like seals and sea lions. Effective surveillance, communication networks, and policy changes are critical to protecting these populations.