Washington confirms first H5N1 detections in dairy cattle

Washington has confirmed its first cases of avian influenza in dairy cattle, adding a new state to the H5N1 livestock map as federal and state officials work to contain the virus in two Yakima County herds. USDA’s National Veterinary Services Laboratories confirmed the detections on October 8, 2026, after the farms reported cattle with clinical signs consistent with highly pathogenic avian influenza. The farms are now under quarantine, and APHIS said sequencing is underway. (aphis.usda.gov)

The development comes after a long stretch in which Washington had avoided confirmed dairy detections despite the broader U.S. cattle outbreak that began in March 2024. USDA said dairy cattle in 19 states have been infected since that outbreak began. Washington’s agriculture department said it and Washington State University’s diagnostic lab had performed more than 7,000 HPAI surveillance tests over the last two years without finding the virus in cattle. Earlier this year, the state had reached an “unaffected” stage under the USDA’s National Milk Testing Strategy, which uses bulk milk and other surveillance tools to identify affected herds and support elimination efforts. (aphis.usda.gov)

The immediate facts are straightforward, but important. The positive herds were identified after showing signs of illness, not solely through routine screening. According to Washington officials, veterinarians are treating sick cows, and most affected cattle recover with supportive care, typically over about six weeks. The state also laid out the clinical signs practitioners should watch for, including thickened or discolored milk, milk drop, fever, respiratory signs, reduced feed intake, manure changes, and a sharp decline in rumination and rumen motility. (agr.wa.gov)

Washington has also published its response framework for a confirmed bovine H5N1 case. That plan calls for quarantine of lactating cows for 21 days after the last newly clinical animal is identified, isolation of clinically ill cows, and restrictions on moving clinically ill or lactating animals off-farm except directly to slaughter. Local health jurisdictions are also expected to monitor exposed farmworkers for symptoms, reflecting the continued One Health approach that has shaped the dairy response since 2024. CDC guidance for veterinarians similarly stresses rapid coordination with state animal and public health officials when H5N1 is suspected in cattle. (cms.agr.wa.gov)

Industry and regulatory messaging remains centered on biosecurity and worker protection. USDA says the National Milk Testing Strategy is meant not just to find infected herds, but also to trigger enhanced biosecurity and lower exposure risk for farmworkers. Federal orders issued in 2024 require testing of lactating dairy cattle before interstate movement and support ongoing milk surveillance nationwide. Washington has separately emphasized that infected cows can shed virus in milk, that raw milk and raw dairy products are unsafe, and that pets should not be fed raw milk or raw animal products from affected settings. Pasteurized milk remains safe, according to USDA and state officials. (direct.aphis.usda.gov)

Why it matters: For veterinary professionals, this is less about a surprise pathogen than a reminder that surveillance status can change quickly, even in a state that had looked clear on repeated testing. The Washington cases highlight the limits of relying on surveillance alone without aggressive attention to clinical recognition, movement controls, and on-farm biosecurity. They also reinforce the central role of practicing veterinarians in spotting early milk and respiratory changes, guiding isolation and supportive care, advising on PPE and worker safety, and helping pet parents on mixed-species properties understand the risks tied to raw milk and raw diets. The fact that the positive herds had previously tested negative under routine surveillance suggests that response plans need to stay operational, not theoretical, in “unaffected” states. (aphis.usda.gov)

What to watch: The next key signals are USDA’s sequencing results, any epidemiologic findings on how the virus reached these herds, and whether Washington reports additional county-level detections. Veterinary teams should also watch for any changes in state movement requirements, surveillance intensity, or farmworker monitoring recommendations as the investigation develops. (aphis.usda.gov)