Two dairy cattle herds in Yakima County have tested positive for H5N1, marking the first confirmed cases of highly pathogenic avian influenza in cattle anywhere in Washington state. The two affected farms are now under quarantine, veterinarians are treating sick cows, and the animals showed signs of illness over the past week, including a drop in milk production.
Labs Confirm Washington's First Cattle Detection
The Washington State Department of Agriculture announced the detections on Thursday, Oct. 8, 2026, according to Capital Press. The U.S. Department of Agriculture National Veterinary Services Laboratory and the state agriculture department jointly confirmed the H5N1 detection, as reported by Yakima Herald. Per TriYakNews, the finding represents the first known detection of the virus in cattle anywhere in the state, arriving despite more than two years of state surveillance that included thousands of tests and found no previously confirmed livestock case.
The two Yakima County farms that are impacted are under quarantine and have employed strict biosecurity measures, the Yakima Herald report notes. Cows showed signs over the past week of the sickness, including a drop in milk production, the same Capital Press report states. The Washington Animal Disease Diagnostic Laboratory at Washington State University took part in the state's ongoing H5N1 surveillance effort alongside the state agriculture department, per TriYakNews.
No Human Cases Confirmed, but Workers Are Being Watched
There are currently no confirmed human cases of avian influenza in Yakima County, the Yakima Herald report states. Still, the Yakima Health District issued a statement saying it was in contact with the dairies and monitoring the health of workers exposed to infected cattle, Capital Press reported. People with close or prolonged contact with infected animals face a higher risk of exposure, according to TriYakNews, and the state agriculture department has recommended increased use of personal protective equipment for people working with potentially infected animals.
Infected cows can shed the virus in their milk, making raw milk and other raw dairy products unsafe for consumption, the Yakima Herald report notes. Pasteurization inactivates H5N1, and milk from affected cows does not enter the commercial food supply, according to TriYakNews, so federal and state officials consider the commercial milk supply safe. Consumers should not drink raw, unpasteurized milk from infected animals, the same report states.
A National Outbreak With a Murky Tally
Washington's detection lands amid a national outbreak that has been building since dairy cattle first tested positive in March 2024. Since then, bird flu has been detected in 1,178 cattle herds across the country, with California reporting the most cases at 773, followed by Idaho with 177, Capital Press reported. Accounts differ on how many states have been touched by the spread: the Yakima Herald report states that dairy cattle in 19 states have been infected since the outbreak began, while a separate report from CIDRAP put the figure at 18 states.
The pace of new detections had slowed in recent weeks. In the 30 days before CIDRAP's report, only one dairy cattle herd, in California, had tested positive for avian flu. That same report described Wisconsin's own first cattle detection, traced to the H5 clade 2.3.4.4b strain and caught through a routine national milk testing program, alongside recent poultry outbreaks that affected 20,900 commercial turkeys in Waseca County, Minnesota, and 19,500 commercial birds in Richland County, North Dakota. Nevada has also reported a detection in dairy cattle in Nye County, with the affected premises quarantined and mandatory testing planned onsite until the herd's status is resolved, according to Nye County, Nevada officials.
What Officials Want Producers and the Public to Know
H5N1 can affect the mammary glands of infected cattle, and infected animals can carry high levels of the virus in their milk, according to TriYakNews. Illness signs linked to the virus include reduced appetite and decreased milk production, and the state agriculture department has urged dairy producers to monitor their cattle closely. Producers who suspect H5N1 in their herds should contact their veterinarian or the Washington State Department of Agriculture, which can be reached at 360-902-1878 or by email at [email protected].
State officials have also emphasized biosecurity when animals are moved between farms or other premises. The USDA is using its national milk testing strategy to monitor dairy herds and the nation's milk supply for H5N1, and the agency is working to complete genetic sequencing that officials say will help trace the source of the Washington virus, per Capital Press. The USDA also offers financial assistance to dairy and livestock producers that can help strengthen on-farm biosecurity, covering costs such as disinfectants, personal protective equipment, wildlife controls, and enhanced cleaning and separation practices, according to TriYakNews.
Federal health officials continue to describe the public health risk from the current H5N1 strain as low, though people with close or prolonged contact with infected animals face a higher risk of exposure. The wide geographic spread of the virus among wild birds, poultry, and mammals including cows could create additional opportunities for people to be exposed, according to the Centers for Disease Control and Prevention. Forty-one human cases have been linked to infected dairy operations.
