California Poultry and Dairy Farms See Drop in Bird Flu Infections, State Officials Report

Approach of Spring Brings Increased Potential for Spread Through Wild Birds

As many as 166 million chickens, turkeys, and ducks have been euthanized in California after becoming infected with highly pathogenic avian influenza, which otherwise causes "a pretty horrendous death," said the state veterinarian, Dr. Annette Jones. | Credit: CDFA

The number of bird flu infections has been dropping among poultry flocks, dairy herds, and dairy workers in California over the past several months, state officials reported on Wednesday to a joint meeting of state Senate agriculture and health committees. New reports continue to come from Southern California dairies, however, and then there’s the approach of spring. Wild birds carry the virus as they migrate during the spring, which is also baby chick season for backyard birders, including herself, observed State Senator Marie Alvarado-Gil, who represents 13 counties across the Sierras and the Central Valley and is vice chair of the Senate Agriculture Committee.

The virus has been swapping genes among domestic poultry and wild birds since at least 2020, leading to the current outbreak among commercial flocks in the U.S. that started in January 2022. Biosecurity precautions are taken by producers and at local chick providers, including Island Seed and Feed in Goleta. Matt Vogel explained that they would have chicks into March but was uncertain after that. Island was doing a lot of education, as they always do, for anyone interested in raising chickens, he said.

“We’ve increased our biosecurity and are addressing likely disease vectors,” Vogel added, by doing things like blocking wild birds from coming inside.

Dr. Annette Jones, who leads California’s Animal Health and Food Safety Services, told state senators on the agriculture and health committees that “The state has standing prohibitions against any products from sick cattle or poultry from entering the human food chain.” | Credit: Courtesy

During the Sacramento hearing, Dr. Annette Jones explained that avian influenza in some form is carried by 10 percent of the wild birds sampled recently, with 10 percent of that number carrying the deadly H5N1 strain. Jones is the director of California’s Animal Health and Food Safety Services Division with direct control over decisions to cull poultry flocks. She spoke along with eight others from health and animal health departments and affected industries during the fast-paced hearing.

“It was a surprise that the virus could get into cows,” Jones said of the first case at a dairy in Texas in March 2024.

California’s state veterinarian Dr. Annette Jones described how some species (circled), like sea lions, cattle, poultry, and minks, spread H5N1 among themselves. In others (not circled), like house cats and mice, skunks, bottlenose dolphins, and goats, the virus stopped in the individual with no spread to others. So far, humans are in the latter category. | Courtesy CDFA/Peacock, T.P., Moncla, L., Dudas, G. *et al.*

Though the virus had infected species like skunk, puma, bear, and raptors, the disease had not spread between individuals. But in sea lions in South America, minks in Europe, and now cattle in the U.S., it progressed from animal to animal. Jones quickly gave a primer on the B- and D-types of H5N1, emphasizing that the D-type swapped virus segments very easily. Though dairy cows have commonly caught the B type from birds, herds in Nevada and Arizona became infected with the D-type. This was a recent development, and the hope was that herd immunity would kick in as the cows recovered, but the implications for human contagion were clear.

After Edward Flores of UC Merced described the range of employer responses to dairy worker illnesses, Santa Barbara’s State Senator Monique Limón, who sits on the Senate Health Committee, remarked that it didn’t seem right to have people who were ill taking care of animals. Flores directs the school’s Community and Labor Center, which interviewed dairy workers in Fresno, Tulare, Kings, and Merced counties. They reported that while some employers supported their workers’ well-being, others ridiculed the need for protective gear or made employees fearful of losing their jobs if they were ill. Nonetheless, dairy workers cared for sick animals, gave them injections, milked sick cows to avoid mastitis — directly exposing themselves to H5N1, which is present in the animals’ mammary glands and milk.

State Senator Monique Limón, a member of the Agriculture Committee, stated that workers who are ill should not care for animals but be allowed sick time. | Credit: Courtesy

Tulare County — which had 490,000 of California’s 1.7 million milk cows in 2024, the most in the state by a long shot — shared Limón’s concern. Karen Elliott, head of Tulare public health, and her team geared up early for the outbreak, distributing protective equipment to dairies and getting ready to test. At one point, they were monitoring 2,000 dairy workers and testing any positive influenza A samples, for Tulare and surrounding counties, for H5. Of the 1,900 samples since September, none so far had tested positive, she said.

If a person with influenza A caught H5N1, said Elliott, it opened the door to human-to-human transmission if the two viruses were to swap any segments that allowed such spread. This is the worry of all public health and agriculture officials.

Currently, 144 dairies in California are affected and 100,000 animals quarantined. This is far fewer than the 679 dairies under quarantine in December. Among poultry producers, 87 chicken, turkey, and duck facilities are under quarantine, and 166 million birds have been euthanized. This has clearly affected milk and egg production and prices.

“The state has standing prohibitions against any products from sick cattle or poultry from entering the human food chain,” said Jones, who is also the state veterinarian. Though cows can recover from H5N1 with supportive care, birds die “a pretty horrendous death,” which is why they are slaughtered when infection is detected. The testing for H5N1 has to be accurate, she said, because of the millions of birds affected. They’d even tried to “depopulate a little bit, but every time, it came back and spread to other birds,” she said.

A new vaccine to protect birds from H5N1 was among the strategies for egg-producing chickens to be funded by a $1 billion commitment from the U.S. Department of Agriculture (USDA), said Dr. Rosemary Sifford, a deputy administrator at the agency and its chief veterinary officer. Sifford said the new U.S. Secretary of Agriculture, Brooke Rollins, stated that bird flu was a high priority for the department. Also funded are biosecurity at farms, disease surveillance, and financial help to poultry and dairy operators. Jones noted that USDA was even funding emergency research, which was unusual.

But any vaccine for birds would encounter export problems, the participants on Wednesday said. On Capitol Hill, the Congressional and Senate Chicken Caucuses sought protection assurances from USDA because chickens vaccinated against avian flu could not be exported, as vaccines can mask the presence of live virus. Though egg-laying chickens could be vaccinated, congressmembers were concerned that U.S. export partners might not accept unvaccinated broilers, or meat chickens.

Jones described how the virus had ruined Christmas for veterinarians and farmers, as successive waves of illness crossed from poultry to cattle to poultry again. They’d determined that virus-laden dust was traveling between farms or sections of farms, carrying disease to new areas. One thing they’d learned was that reducing the viral load at farms was necessary to avoid overwhelming the animals’ immune protections or the biosecurity established on the farms.

The current outbreak is killing more wild birds compared to previous bouts with the H5 virus, which raised a whole new set of questions, the USDA’s Sifford said. Wildlife services were mapping detections across the four major U.S. flyways to get as early a start as possible.

“How is the virus persisting season after season, killing some but not others?” she asked. “This is a question we are keenly interested in.”

Correction: This article was updated to note that USDA was investing in a “strategy for new generation vaccines, therapeutics, and other innovative solutions” to avoid depopulating egg-producing chickens. This includes limiting export impacts.