- USDA has confirmed highly pathogenic avian influenza (HPAI) H5 clade 2.3.4.4b in two dairy cattle herds in Washington, marking the state’s first confirmed livestock detections.
- The infections were identified through PCR testing after cattle exhibited clinical signs consistent with avian influenza, despite previously testing negative under the National Milk Testing Strategy.
- Washington becomes the 19th state to report HPAI infections in dairy cattle since the outbreak began in March 2024.
- USDA and Washington animal health officials are conducting additional diagnostic testing, on-farm investigations and epidemiological assessments to determine the circumstances surrounding the detections.
- Federal officials say the commercial pasteurized milk supply remains safe and that the risk to the general public is low, although individuals with occupational exposure to infected animals face elevated risks.
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) has confirmed highly pathogenic avian influenza (HPAI) in two dairy cattle herds in Washington, representing the state’s first confirmed detections of the virus in livestock.
The October 8 announcement follows polymerase chain reaction (PCR) testing conducted by USDA’s National Veterinary Services Laboratories (NVSL), which detected H5 clade 2.3.4.4b in both herds.
According to APHIS, the affected cattle were tested after developing clinical signs consistent with avian influenza. Both herds had previously returned negative results through routine surveillance conducted under USDA’s National Milk Testing Strategy.
Federal officials are completing genetic sequencing to further characterize the virus and expect to release additional findings when available.
First Livestock Detections in Washington
The detections expand the geographic footprint of HPAI in U.S. dairy cattle, which were first confirmed to be infected with the virus in March 2024.
With the addition of Washington, dairy herds in 19 states have experienced confirmed infections since the outbreak began, although USDA reports that detections during 2026 have been limited to a relatively small number of states.
APHIS is coordinating with the Washington State Department of Agriculture to investigate the affected premises and assess potential pathways of virus introduction and transmission.
The investigation includes additional on-farm diagnostic testing, epidemiological data collection and efforts to identify potential connections between infected animals, premises and other possible sources of exposure.
The agency has not yet released final genetic sequencing results or detailed findings regarding how the virus entered the affected herds.
USDA Emphasizes Biosecurity and Early Detection
Despite the new detections, USDA says its existing HPAI eradication strategy for dairy cattle remains unchanged.
APHIS continues to emphasize enhanced farm biosecurity, surveillance and prompt reporting of suspected infections as central components of its response.
Dairy producers are encouraged to strengthen measures intended to prevent virus introduction and movement between premises, including managing animal movements, limiting potential exposure to infected wildlife and maintaining appropriate sanitation practices.
USDA also advises producers to report livestock exhibiting clinical signs consistent with HPAI, as well as unusual illness or mortality among wildlife, to their state veterinarian.
Financial assistance remains available through USDA programs to support enhanced biosecurity and help offset certain costs associated with HPAI prevention and response.
Additional information about these resources is available through the USDA HPAI livestock response program.
Commercial Milk Supply Remains Safe
USDA emphasized that the Washington detections do not affect the safety of the commercial pasteurized milk supply.
The U.S. Food and Drug Administration maintains that pasteurization is effective at inactivating HPAI virus, and federal officials continue to consider commercially pasteurized milk safe for consumers.
Dairy operations are required to ensure that only milk from healthy animals enters processing for human consumption. Milk from affected cattle must be diverted from the commercial supply or destroyed.
The Centers for Disease Control and Prevention (CDC) continues to assess the risk posed by HPAI viruses circulating in birds and U.S. dairy cattle as low for the general public.
However, people with occupational or recreational exposure to infected birds or mammals, including dairy workers, veterinarians and others handling potentially infected animals, face an increased risk of infection.
CDC recommends appropriate personal protective equipment and other preventive measures for individuals who may encounter infected animals or contaminated environments.
Continued Surveillance and Investigation
The Washington detections highlight the importance of ongoing dairy herd surveillance, particularly when animals develop clinical signs despite previous negative screening results.
USDA’s National Milk Testing Strategy remains a component of federal efforts to monitor HPAI circulation in dairy cattle and identify infections that could otherwise go undetected.
APHIS and Washington animal health officials will continue diagnostic testing and epidemiological investigations while evaluating measures to limit further transmission.
Updated information about confirmed HPAI detections in livestock is available through USDA’s HPAI livestock case reporting page.
Information sourced from the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) announcement dated October 8, 2026.
