CDFA: H5N1 outbreak in California dairies and poultry is large but slowing; state steps up testing, research and animal-response coordination

The California Department of Food and Agriculture (CDFA) told the Veterinary Medical Board on Jan. 14 that highly pathogenic avian influenza H5N1 has infected hundreds of dairy operations and tens of millions of birds this season, but that new detections have fallen in recent weeks.

“Right now, we are on the downside of our epi curve. The number of new detections is quite a bit lower now per week,” Dr. Annette Jones, CDFA assistant deputy director for animal health, told the board. She added that the downward trend partly reflects immunity across many herds and that testing over the winter holidays briefly reduced reported detections.

Why it matters: The outbreak has affected both agriculture and companion-animal sectors — prompting broad testing programs, quarantine orders, and research to understand how the virus behaves in a new host (dairy cattle) and how to limit spillover into poultry, pets and people.

What CDFA reported

- Dairies and milk testing: CDFA said it has recorded a cumulative total of 736 positive dairies (the department counts presumptive as well as confirmed cases). Some dairies have cleared quarantine after three consecutive weeks of negative bulk-milk tests; CDFA reported about 627 dairies remained under state quarantine at the time of the board meeting and “over a hundred” had been released.

- Surveillance scale: CDFA is submitting roughly 1,400 samples weekly for dairy surveillance to the California Animal Health and Food Safety Laboratory System and other certified labs. For poultry, the department reported sending about 1,200 routine surveillance tests and hundreds more of environmental and movement-control tests in a typical recent week.

- Animal losses: Dr. Jones told the board the current poultry wave has been the state’s largest on record. She said the most recent three-month period has seen 10.4 million laying hens removed (either dead or euthanized), compared with about 4 million in the prior major outbreak, with similarly large increases in broilers and turkeys. (CDFA’s slide presentation gave outbreak loss figures by species.)

- Virus behavior in cows: CDFA said the virus behaves differently in cows than in poultry — it spreads readily among cows (high morbidity) but appears to cause relatively low mortality unless animals have other health problems. CDFA officials said milk (bulk-tank) testing is the most sensitive surveillance sample for detecting the virus in dairy herds; nasal swabs and urine are less reliable, although some herds have yielded detectable virus in serum and urine.

- Zoonotic risk and worker protection: CDFA said the human cases identified in California have been associated primarily with dairy workers and have mostly involved conjunctivitis. The department said it and public-health partners are working to protect dairy workers, including distributing eye protection, N95 masks and other personal protective equipment through public-health and Cal/OSHA channels and coordinating monitoring of exposed workers with public-health authorities.

- Research: CDFA said it is coordinating dozens of research projects to better understand transmission, the role of milk and the environment, and the ecology of the virus in cattle. The department has redirected epidemiology and antimicrobial stewardship staff to support the emergency response and research coordination, and it is funding longitudinal herd studies with academic partners.

Poultry specifics and control measures

CDFA described movement-control areas and mandatory testing around infected poultry flocks, plus environmental testing and a stepwise process for permitting farms to restock after cleaning and negative tests. CDFA said 61 poultry movement-control areas had been established and 33 had been released. Environmental sampling of barns is used to permit restocking once results are negative.

CDFA also said whole-genome sequencing shows some poultry infections are linked to nearby infected dairies; other poultry infections trace to wild-bird introductions. The department ranked both sources as threats to poultry flocks.

Disaster response: wildfires and animals

CDFA briefed the board separately on wildfire response and animal evacuation logistics. Dr. Jones said California coordinates animal and agriculture needs under Emergency Support Function 11, and that CDFA works with UC Davis and the Governor’s Office of Emergency Services to coordinate resources, sheltering, and volunteer teams (Community Animal Response Teams and university-run CVET teams) during disasters. She urged volunteers not to self-deploy and said CDFA maintains situational awareness for fairgrounds and shelter capacity.

Board and public reaction

Board members asked how CDFA’s laboratories and staff were managing the surge; Dr. Jones said the department is tapping USDA surge capacity, reallocating state staff and exploring whether additional sustained resources are needed. Board members also pressed CDFA on raw-milk and raw-pet-food risks; Dr. Jones told the board pasteurization inactivates the virus and that CDFA has increased testing and temporary diversion-to-pasteurization requirements for raw-milk producers in high-risk areas.

Public comments to the board raised concerns about pets and raw pet food; CDFA staff said the department would communicate with veterinarians and the public about raw-food risks and the need to source raw products from licensed suppliers.

What the board will do next

CDFA said it will continue to coordinate testing, research and outreach and that state and federal partners remain engaged. The Veterinary Medical Board asked CDFA to keep the board informed as research and policy decisions progress.

Provenance (excerpt from meeting transcript): - "I'm gonna give a quick update of a couple of things happening at the California Department of Food and Agriculture..." — Dr. Annette Jones (transcript excerpt). - "We submit on a weekly basis about 1,400 samples to the laboratory in Davis..." — Dr. Annette Jones (transcript excerpt).