A highly pathogenic strain of bird flu has been confirmed in northern elephant seals at California’s Año Nuevo State Park, marking a first for the species and the state’s marine mammals.

Researchers announced that seven weaned elephant seal pups tested positive for HPAI H5N1, according to a joint statement from scientists at the University of California, Davis and UC Santa Cruz reported by UC University News. The discovery followed observations of sick and dead animals with respiratory and neurological signs earlier this month.

About 30 elephant seals, mostly young pups, have died in the outbreak, according to authorities tracking the situation at Año Nuevo, a major winter breeding colony, UC University News reports. More test results are pending.

Public health officials say the risk to humans remains low, but they urge caution and recommend keeping pets away from infected animals as the outbreak unfolds, according to SFGate.

H5N1 has been confirmed in northern elephant seals in California.

Rapid Detection in a Vulnerable Colony

The H5N1 virus was identified by the U.S. Department of Agriculture’s National Veterinary Services Laboratory after weeks of heightened surveillance, scientists told UC University News. Researchers have been watching this and other marine mammal populations closely since H5N1 spread through seabirds and wildlife across the Americas.

About 1,350 seals were present on the beach when the outbreak began, and roughly 5,000 typically congregate there each season, UC University News reports. The dense gatherings make early detection crucial.

Experts said early detection likely came from long-term monitoring efforts by scientists who patrol the beach almost daily during breeding seasons.

The outbreak marks the first known cases in the species.

Tours Cancelled, Viewing Areas Closed

In response to the outbreak, California State Parks has closed the main seal-viewing areas at Año Nuevo and canceled guided tours for the remainder of the season, AP News reports. The closures aim to reduce human disturbance and any potential health risks.

Officials have also advised visitors to stay at least 150 yards from seals and never touch live or dead wildlife, according to The Marine Mammal Center.

Echoes of Past Outbreaks

H5N1 has shown an ability to jump species and cause high mortality in wildlife before. In 2023, outbreaks in South America decimated southern elephant seal and sea lion populations, killing thousands and prompting closer surveillance worldwide, as chronicled in outbreak histories of H5N1’s spread across continents.

The virus has been detected in a range of mammals over the past few years, including farmed mink and other wild mammals, heightening concerns about its adaptability.

Año Nuevo State Park hosts thousands of breeding seals each winter.

Scientists Watch Closely

While most of the colony appears healthy, researchers continue to monitor animals for signs of infection and consult with wildlife agencies to track the disease’s path. The coming weeks will be critical in understanding whether the outbreak remains limited or expands within the seal population.