An HPAI infection at an unnamed Stanislaus County egg ranch resulted in the loss of 1.3 million hens. The case is notable for its scale and comes amid reports of infections in poultry and dairy herds in several states.
The USDA figure was reported by the Hanford Sentinel in a November 6 article, which said the discovery was reported on October 28. The Sentinel described it as California's first commercial-poultry detection of the fall and the state's largest such outbreak in more than a year. The ranch's name has not been made public.
A Pattern of Backyard and Commercial Cases
Three backyard flocks in California tested positive earlier in October, according to the Sentinel's report. It also reported new bird-flu cases in dairy cows in Washington State and Colorado within the past week.
California's recent commercial-flock cases include a raised-for-release upland game bird flock in Butte County in January and a broiler flock in Sonoma County in February, where roughly 86,000 birds were affected, according to the Sentinel. Infected birds are culled as a measure to limit further spread.
What agencies say about detection and possible sources
A separate California commercial-flock case was announced in Fresno County on August 22, 2022, by the California Department of Food and Agriculture and USDA APHIS. The announcement confirms a detection but does not establish the source of infection in the Stanislaus County flock. The California Department of Food and Agriculture says wild birds—especially waterfowl such as ducks and geese—can spread avian influenza. That general guidance does not confirm that wild birds infected this particular flock, according to the California Department of Food and Agriculture.
Beyond California's Borders
Oregon has also reported a commercial egg-layer flock infection: 94,200 birds were euthanized at an operation in Clackamas County, according to The Bulletin. The outlet reported increased cases this fall in California and the Pacific Northwest, where HPAI detections tend to rise in fall and spring as wild waterfowl migrate. It also reported that 40 dairy herds in Central Washington caught HPAI within the past month.
The Stanislaus loss is not the only large commercial layer-flock case reported nationally this fall. A flock of 934,600 hens in Clinton County, Illinois, was confirmed infected on October 9, according to WATTPoultry.com.
The Bigger Picture for Egg Prices and Flocks
Since 2022, about 210 million birds in U.S. commercial stocks have been culled or have died because of avian influenza, the Sentinel reported. California's outbreaks have affected more than 17 million chickens, many in the Central Valley, and contributed to sharply higher egg prices in 2024 and 2025. The latest loss adds to the pressure on poultry flocks as cases recur.
