A study from the University of California, Davis, published on Mar. 19, examines the worldwide impact of highly pathogenic avian influenza (H5N1) on pinnipeds—seals and sea lions—and offers recommendations for monitoring and protecting these species. The research highlights that since its discovery in Asia in 1996, H5N1 has spread globally, infecting more than 400 million poultry, thousands of marine mammals including elephant seals and sea lions, about 1,000 people, and many other wild birds.
The issue is significant because pinnipeds have been severely affected by the virus. Outbreaks across South America have resulted in at least 36,000 South American sea lion deaths, along with thousands of southern elephant seals and South American fur seals. The study aims to help prevent the virus from reaching vulnerable but currently unaffected species such as the endangered Hawaiian monk seal or Galapagos sea lion.
“There is a huge, unprecedented conservation risk,” said Christine Johnson, director of the Institute for Pandemic Insights at UC Davis Weill School of Veterinary Medicine. “Influenza is constantly changing, and that is a big problem now that it’s widely circulating in birds and marine mammals.”
Marcela Uhart, a veterinarian with UC Davis’s Karen C. Drayer Wildlife Health Center Latin America Program and co-author of the study, described witnessing a major outbreak among southern elephant seals in Argentina in 2023. “Southern elephant seals were the canary in the coal mine alerting us to a bigger issue of pinnipeds throughout the entire world,” said Uhart. “We can do something better to be prepared the next time before it spreads to other species.”
In California, northern elephant seals marked their first cases of HPAI H5N1 after routine surveillance was established by UC Davis and partners over a year prior. Increased surveying efforts began at Año Nuevo Natural Reserve following rising cases among Bay Area seabirds at the end of 2025. This allowed for rapid detection during breeding season outbreaks.
Key recommendations from the paper include funding long-term wildlife monitoring; building stronger communication networks among researchers; making wildlife health surveillance routine; improving non-invasive monitoring technologies; pursuing policy changes addressing root causes; and tackling concurrent threats like habitat loss and climate change.
“H5 avian influenza viruses are an emergent threat to seal and sea lion populations already facing numerous conservation pressures,” said Elizabeth Ashley, first author and graduate student researcher at UC Davis. “Understanding how this virus spreads in coastal ecosystems is critical for protecting vulnerable marine wildlife.”
The research was supported by grants from organizations including the US National Science Foundation Center for Pandemic Insights.
