Deadly virus first detected in Bay Area park found in Central California

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A strain of the deadly avian flu that was first detected in Ano Nuevo State Park last month has now been confirmed in a dead California sea lion found on a beach in San Luis Obispo County, hundreds of miles south of the initial outbreak. This is the first report of the HPAI H5N1 virus in a marine mammal from San Luis Obispo County, and researchers are continuing to monitor marine mammal populations along the central California coast.

Why it matters

The spread of this highly pathogenic avian influenza (HPAI) virus to marine mammals is concerning, as it demonstrates the virus's ability to cross species boundaries and potentially impact a wider range of wildlife. Public health officials are warning people to avoid approaching sick or injured marine mammals and seabirds, as the risk of transmission to humans, though low, remains a possibility.

The details

The latest case was confirmed by UC Davis and the USDA's National Veterinary Services lab on March 25. The infected sea lion, approximately one to two years old, was found along Morro Strand State Beach in Morro Bay. This is the third known case of a sea lion contracting the virus since the start of the outbreak, with the other two found in San Mateo County. Researchers are continuing to monitor marine mammal populations all along the central California coast, as juvenile sea lions are known to forage in the region.

• The virus was first detected in Ano Nuevo State Park last month.
• On March 16, the latest case was sampled by a researcher from the Central California Marine Animal Response Team (CCMART).
• On March 25, the case was confirmed by UC Davis and the USDA's National Veterinary Services lab.
• Earlier this month, the virus was detected for the first time at Point Reyes National Seashore in a dead common murre.
• Public health officials said positive cases of bird flu were first confirmed in San Luis Obispo County in 2022.

What’s next

Researchers are continuing to monitor marine mammal populations all along the central California coast for any additional cases of the HPAI H5N1 virus.