Researchers say the H5N1 bird flu outbreak in California elephant seals has spread to other marine mammals, including a sea otter and sea lion.

However, wildlife officials are cautiously optimistic the outbreak will remain contained. It has so far only been detected on beaches in San Mateo County, although testing is being conducted along the coastline.

The strain the animals have contains a mutation allowing it to more easily transmit between mammals. It is also a different variation than the ones found in dairy cows and commercial poultry. This one is Eurasian in origin, first seen in 2022. It has been detected in birds that fly along the Pacific Flyway, and is responsible for a mass mortality event in 2023 in northern fur seals on an island in eastern Russia, said Christine Johnson, director of UC Davis’ Center for Pandemic Insights, during a press conference Thursday morning.

Johnson said researchers think this is the first detection of the A3 variation of the virus on the Pacific Coast and therefore likely a new introduction into North America, she said.

In late February, a team of researchers from UC Davis, UC Santa Cruz, the California Department of Fish and Wildlife and the Marine Mammal Center announced they had found the virus in seven dead elephant seal pups collected from the beach at Año Nuevo State Park. That number is now 16, but Johnson said likely more will be confirmed in the weeks to come.

“This count reflects only the animals that have gone through sampling and confirmatory testing in multiple labs,” she said. “We know there are more animals with signs of infection that we have sampled that are being tested across the different laboratory systems.”

She said no other otters have been found, but a “handful” of California sea lions are “in the queue.” This kind of spillover, she said, is not unusual.

“Outbreaks affect a wide range of birds and mammals, and these animals all share the near shore ecosystem,” she said, although it’s “especially tragic” when infections affect less common species in the southern sea otter.

Patrick Robinson, the Año Nuevo reserve director, and a marine biologist at UC Santa Cruz, said 47 elephant seals on the mainland have died since the outbreak began, and the wildlife team is finding two new symptomatic and two dead animals every day.

Symptoms of bird flu in mammals include tremors, convulsions, seizures and muscle weakness.

He said it is normal for some individuals to die of natural causes, so testing is critical. And he said the percentage of animals that have died in the Año Nuevo rookery is relatively small: Only about 5% of weaned pups and 6% of adult males have died. Still, in the case of pups, that’s four times higher than last year’s death rates. And he said, the death of large males is “basically nonexistent in most males.”

He said 80% of the adult females had departed by the time the outbreak began, and nearly all of them are now gone. No adult females have died, and none have been observed with symptoms.

“The outbreak is not over, and we’re not really sure what’s going to happen in the future,” he said. “I remain hopeful about this thing right now.”

In late 2022, the H5N1 bird flu virus decimated southern elephant seal populations in South America and several sub-Antarctic Islands. At some colonies in Argentina, 97% of pups died, while on South Georgia Island, researchers reported a 47% decline in breeding females between 2022 and 2024. Researchers believe tens of thousands of animals died.

More than 30,000 sea lions in Peru and Chile died between 2022 and 2024. In Argentina, roughly 1,300 sea lions and fur seals perished.

At the time, researchers were not sure why northern Pacific populations were not infected, but suspected previous or milder strains of the virus conferred some immunity.

The virus is better known in the U.S. for sweeping through dairy herds, where it infected dozens of dairy workers, millions of cows and thousands of wild, feral and domestic mammals. It’s also been found in wild birds and killed millions of commercial chickens, geese and ducks.

Two Americans have died from the virus since 2024, and 71 have been infected. The vast majority of infected people were dairy or commercial poultry workers. One death was that of a Louisiana man who had underlying conditions and was believed to have been exposed via backyard poultry or wild birds.

A new report shows that nearly 40% of conventionally grown fruits and vegetables tested by California regulators have residues of “forever” or PFAS chemicals, a family of compounds that can be lasting and harmful.

The Environmental Working Group, an advocacy group based in Washington, D.C., reviewed California’s own test data and found PFAS pesticide residues on peaches, grapes and strawberries, and about three dozen other types of fruits and vegetables.

The chemicals have have increasingly been used in agricultural chemicals in recent years.

“Here’s the thing: This is an emerging threat,” said Nathan Donley, environmental health science director for the Center for Biological Diversity, who was not involved in the report. “PFAS pesticides went from being the exception to now they’re the rule.”

More than 90% of nectarine, peach and plum samples tested contained the PFAS fungicide fludioxonil. The fungicide is sprayed on the fruits after harvest to prevent mold. More than 80% of the cherries, strawberries and grapes sampled carried PFAS residue.

The group relied on data collected in 2023 by California’s Department of Pesticide Regulation, a branch of CalEPA.

There are thousands of PFAS chemicals used in consumer products, electronics, pharmaceuticals and pesticides. They are prized by product manufacturers for their strength, persistence and water resistance. However, many are considered highly toxic, even at very low levels. They’ve been linked to immune suppression, cancer and reproductive and developmental health disruptions and toxicity. They’ve also been linked to ecosystem damage, harming aquatic animals and wildlife.

The vast majority of PFAS chemicals have not been tested for human health effects.

“At a time when most industries are transitioning away from PFAS chemicals, the pesticide industry is actually doubling down on them,” said Donley, who has published papers on the issue. “I think that the persistence of these chemicals is certainly playing a role” in why industries find them desirable, he said.

“But then again, you get a whole heck of a lot more collateral damage when you have a pesticide that sticks around as long as DDT does,” he said.

Regulators say that not all PFAS chemicals are the same. While some can persist for thousands of years, others break down much more quickly. They also say the ones used in approved pesticides are vetted for human health impacts, as well as ecosystem impacts — such as how they could affect pollinators, aquatic organisms and other wildlife. There are also strict usage requirements that limit the amount of chemicals applied to food, they say.

“Before any pesticide can be sold or used in California, DPR (Department of Pesticide Regulation) conducts a thorough scientific review. This includes evaluating both the active ingredients and full product formulations to understand how long the chemicals remain in the environment and how they break down, which is a key concern for PFAS compounds,” said Amy MacPherson, a spokeswoman for the pesticide agency.

In addition, she said, while the report looks at “detections” of PFAS chemicals, her agency “looks at how those detections compare to federal tolerance levels.”

She said this is important because “detection alone … does not necessarily mean there’s a health risk. Tolerance levels consider lifelong, daily exposure that pose a reasonable certainty of no harm, inclusive of chronic risk.”

Varun Subramaniam, a co-author of the report and a health data specialist with the Environmental Working Group, said he focused on California for two reasons: California’s pesticide department is one of the few, if not only, state agencies to do this kind of testing; and the state is one of the nation’s largest producers of fruits and vegetables.

“Things that are grown in California tend to spread across the country,” said Subramaniam, who is working on a national report documenting the use of these pesticides. “We thought California was a good starting point.”

Roughly 70 PFAS pesticides are registered with the U.S. Environmental Protection Agency, accounting for about 14% of all active pesticide ingredients. California has registered 53 PFAS pesticides.

According to the report, about 2.5 million pounds of PFAS pesticides are applied annually on California cropland.

Both Subramaniam and Donley said states such as Maine, Rhode Island, Minnesota and North Carolina are “way ahead” of California in considering the harm these chemicals pose to people and ecosystems, and are trying to ban them.

“These chemicals are really top of mind in the East Coast, especially in New England states where … this story has been going on for decades,” he said.

Subramaniam said people should wash their produce before eating, and opt for organic fruits and vegetables when they can — organic farmers cannot use these chemicals on their produce.

SACRAMENTO — California Gov. Gavin Newsom has positioned himself as a national public health leader by staking out science-backed policies in contrast with the Trump administration.

After Health and Human Services Secretary Robert F. Kennedy Jr. fired Centers for Disease Control and Prevention Director Susan Monarez for refusing what her lawyers called “the dangerous politicization of science,” Newsom hired her to help modernize California’s public health system. He also gave a job to Debra Houry, the agency’s former chief science and medical officer, who had resigned in protest hours after Monarez’s firing.

Newsom also teamed up with fellow Democratic governors Tina Kotek of Oregon, Bob Ferguson of Washington and Josh Green of Hawaii to form the West Coast Health Alliance, a regional public health agency, whose guidance the governors said would “uphold scientific integrity in public health as Trump destroys” the CDC’s credibility. Newsom argued establishing the independent alliance was vital as Kennedy leads the Trump administration’s rollback of national vaccine recommendations.

More recently, California became the first state to join a global outbreak response network coordinated by the World Health Organization, followed by Illinois and New York. Colorado and Wisconsin signaled they plan to join. They did so after President Trump officially withdrew the United States from the agency on the grounds that it had “strayed from its core mission and has acted contrary to the U.S. interests in protecting the U.S. public on multiple occasions.” Newsom said joining the WHO-led consortium would enable California to respond faster to communicable disease outbreaks and other public health threats.

Although other Democratic governors and public health leaders have openly criticized the federal government, few have been as outspoken as Newsom, who is considering a run for president in 2028 and is in his second and final term as governor. Members of the scientific community have praised his effort to build a public health bulwark against the Trump administration’s slashing of funding and scaling back of vaccine recommendations.

What Newsom is doing “is a great idea,” said Paul Offit, an outspoken critic of Kennedy and a vaccine expert who formerly served on the Food and Drug Administration’s vaccine advisory committee but was removed under Trump in 2025.

“Public health has been turned on its head,” Offit said. “We have an anti-vaccine activist and science denialist as the head of U.S. Health and Human Services. It’s dangerous.”

The White House did not respond to questions about Newsom’s stance and Health and Human Services declined requests to interview Kennedy. Instead, federal health officials criticized Democrats broadly, arguing that blue states are participating in fraud and mismanagement of federal funds in public health programs.

Health and Human Services spokesperson Emily Hilliard said the administration is going after “Democrat-run states that pushed unscientific lockdowns, toddler mask mandates, and draconian vaccine passports during the COVID era.” She said those moves have “completely eroded the American people’s trust in public health agencies.”

Public health guided by science

Since Trump returned to office, Newsom has criticized the president and his administration for engineering policies that he sees as an affront to public health and safety, labeling federal leaders as “extremists” trying to “weaponize the CDC and spread misinformation.” He has excoriated federal officials for erroneously linking vaccines to autism, warning that the administration is endangering the lives of infants and young children in scaling back childhood vaccine recommendations. And he argued that the White House is unleashing “chaos” on America’s public health system in backing out of the WHO.

The governor declined an interview request, but Newsom spokesperson Marissa Saldivar said it’s a priority of the governor “to protect public health and provide communities with guidance rooted in science and evidence, not politics and conspiracies.”

The Trump administration’s moves have triggered financial uncertainty that local officials said has reduced morale within public health departments and left states unprepared for disease outbreaks and prevention efforts. The White House last year proposed cutting Health and Human Services spending by $33 billion, including $3.6 billion from the CDC. Congress largely rejected those cuts last month, although funding for programs focusing on social drivers of health, such as access to food, housing and education, were axed.

The Trump administration announced that it would claw back more than $600 million in public health funds from California, Colorado, Illinois and Minnesota, arguing that the Democratic-led states were funding “woke” initiatives that didn’t reflect White House priorities. Within days, the states sued and a judge temporarily blocked the cut.

“They keep suddenly canceling grants and then it gets overturned in court,” said Kat DeBurgh, executive director of the Health Officers Assn. of California. “A lot of the damage is already done because counties already stopped doing the work.”

Federal funding has accounted for more than half of state and local health department budgets nationwide, with money going toward fighting HIV and other sexually transmitted infections, preventing chronic diseases, and boosting public health preparedness and communicable disease response, according to a 2025 analysis by KFF, a health information nonprofit that includes KFF Health News.

Federal funds account for $2.4 billion of California’s $5.3-billion public health budget, making it difficult for Newsom and state lawmakers to backfill potential cuts. That money helps fund state operations and is vital for local health departments.

Funding cuts hurt all

Los Angeles County public health director Barbara Ferrer said if the federal government is allowed to cut that $600 million, the county of nearly 10 million residents would lose an estimated $84 million over the next two years, in addition to other grants for prevention of HIV and other sexually transmitted infections. Ferrer said the county depends on nearly $1 billion in federal funding annually to track and prevent communicable diseases and combat chronic health conditions, including diabetes and high blood pressure. Already, the county has announced the closure of seven public health clinics that provided vaccinations and disease testing, largely because of funding losses tied to federal grant cuts.

“It’s an ill-informed strategy,” Ferrer said. “Public health doesn’t care whether your political affiliation is Republican or Democrat. It doesn’t care about your immigration status or sexual orientation. Public health has to be available for everyone.”

A single case of measles requires public health workers to track down 200 potential contacts, Ferrer said.

The U.S. eliminated measles in 2000 but is close to losing that status as a result of vaccine skepticism and misinformation spread by vaccine critics. The U.S. had 2,281 confirmed cases last year, the most since 1991, with 93% in people who were unvaccinated or whose vaccination status was unknown. This year, the highly contagious disease has been reported at schools, airports and Disneyland.

Public health officials hope the West Coast Health Alliance can help counteract Trump by building trust through evidence-based public health guidance.

“What we’re seeing from the federal government is partisan politics at its worst and retaliation for policy differences, and it puts at extraordinary risk the health and well-being of the American people,” said Georges Benjamin, executive director of the American Public Health Assn., a coalition of public health professionals.

Robust vaccine schedule

Erica Pan, California’s top public health officer and director of the state Department of Public Health, said the West Coast Health Alliance is defending science by recommending a more robust vaccine schedule than the federal government. California is part of a coalition suing the Trump administration over its decision to rescind recommendations for seven childhood vaccines, including for hepatitis A, hepatitis B, influenza and COVID-19.

Pan expressed deep concern about the state of public health, particularly the uptick in measles. “We’re sliding backwards,” Pan said of immunizations.

Sarah Kemble, Hawaii’s state epidemiologist, said Hawaii joined the alliance after hearing from pro-vaccine residents who wanted assurance that they would have access to vaccines.

“We were getting a lot of questions and anxiety from people who did understand science-based recommendations but were wondering, ‘Am I still going to be able to go get my shot?’” Kemble said.

Other states led mostly by Democrats have also formed alliances, with Pennsylvania, New York, New Jersey, Massachusetts and several other East Coast states banding together to create the Northeast Public Health Collaborative.

Hilliard, of Health and Human Services, said that even as Democratic governors establish vaccine advisory coalitions, the federal Advisory Committee on Immunization Practices “remains the scientific body guiding immunization recommendations in this country, and HHS will ensure policy is based on rigorous evidence and gold standard science, not the failed politics of the pandemic.”

Influencing red states

Newsom, for his part, has approved a recurring annual infusion of nearly $300 million to support the state Department of Public Health, as well as the 61 local public health agencies across California, and last year signed a bill authorizing the state to issue its own immunization guidance. It requires health insurers in California to provide patient coverage for vaccinations the state recommends even if the federal government doesn’t.

Jeffrey Singer, a doctor and senior fellow at the libertarian Cato Institute, said decentralization can be beneficial. That’s because local media campaigns that reflect different political ideologies and community priorities may have a better chance of influencing the public.

A KFF analysis found some red states are joining blue states in decoupling their vaccine recommendations from the federal government’s. Singer said some doctors in his home state of Arizona are looking to more liberal California for vaccine recommendations.

“Science is never settled, and there are a lot of areas of this country where there are differences of opinion,” Singer said. “This can help us challenge our assumptions and learn.”

KFF Health News is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF — the independent source for health policy research, polling and journalism.