A dead sea lion found along Morro Strand State Beach in San Luis Obispo County has tested positive for H5N1 — also known as avian influenza or, more commonly, bird flu.

It’s the first confirmed case in a marine mammal in the county, according to a news release from the Public Health Department on Friday afternoon.

According to a separate UC Davis release, the 1- to 2-year-old sea lion was sampled by a researcher from Central California Marine Animal Response Team on March 16, and samples were sent to UC Davis and the U.S. Department of Agriculture’s lab, where presence of the virus was confirmed Wednesday.

That comes after an outbreak of the bird flu among marine mammals in San Mateo County earlier this month that left several elephant seal pups dead.

Local experts have since been keeping a close eye on that outbreak to see if it could spread to San Luis Obispo County and elsewhere in California.

The dead sea lion is the first marine mammal outside of the San Mateo County outbreak to test positive for the flu, according to the UC Davis release.

“Juvenile sea lions are known to forage along the central California coast, traveling as far south as the primary sea lion breeding colonies on the Channel Islands,” the release said. “Researchers are continuing to monitor marine mammal populations all along the coast.”

The risk to local marine mammals hasn’t changed much since the Morro Bay sea lion tested positive for the avian flu, Central California Marine Animal Response Team Executive Director Barbie Halaska told The Tribune.

Since the start of the San Mateo County outbreak in February, Halaska has taken samples from 11 northern elephant seals, three sea lions and one sea otter. Of those samples, only the one sea lion tested positive for the flu, she said.

Halaska and fellow researchers don’t think this sea lion indicates the start of a local avian flu outbreak.

“We think it’s just a one-off,” she said.

Local researchers have been monitoring for the avian flu since 2023, when an outbreak of the virus decimated an elephant seal population in the Valdés Peninsula in Argentina. The flu is more likely to pass from infected bird guano to marine mammals — a risk that hasn’t changed. The virus is far less likely to spread between marine mammals, she said.

Halaska continues to wear a mask, gloves and goggles to protect herself while taking samples, and she wears rubber boots that she can disinfect between beaches. She hasn’t changed her protocols since the sea lion tested positive, she said.

What to Do If You See a Sick or Dead Marine Mammal in SLO County

According to the county release, the risk of bird flu to the public remains low, but officials are urging community members to avoid approaching marine mammals and seabirds, especially those that appear sick, injured or deceased.

People should stay at least 150 yards away from and keep children and pets away from any sick or dead wildlife, the release said.

Anyone who spots a sick, injured or dead marine mammal is asked to call the NOAA West Coast Marine Mammal Stranding Hotline at 866.767.6114 or the California Department of Fish and Wildlife at 916.358.2790 for assistance with birds.

According to the release, positive cases of bird flu have been found in SLO County from various wild birds since 2022. In 2024, California and other states saw outbreaks of H5N1 in dairy cattle. There were 38 confirmed human cases in California linked to exposures from infected cattle between September 2024 and January 2025.

There were no human cases of bird flu in humans in SLO County during that time, the release said.

“While the risk to the public remains low, it’s understandable that people may have questions about their own health if they find themselves unexpectedly exposed to a sick or dead animal,” County Health Officer Dr. Penny Borenstein said in the release.

“If community members have questions about H5N1 as it relates to human health, our Public Health Department can help answer those questions.”

Community members can reach the Public Health Department by calling 805.781.5500.

More information on the bird flu can also be found at the California Department of Public Health’s website at cdph.ca.gov/Programs/CID/DCDC/pages/Bird-Flu.aspx. UC Davis also routinely provides updates on recent H5N1 activity in marine mammals at pandemicinsights.ucdavis.edu/h5-marine-outbreak.