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…