Washington state has gone from zero confirmed cases of highly pathogenic avian influenza (HPAI), also known as H5N1, in dairy cattle to nine infected herds in a matter of weeks. The detections began Oct. 8 in Yakima County and have since spread to a second county, despite more than 7,000 negative surveillance tests over the previous two years.
The Washington State Department of Agriculture confirmed the latest case Oct. 26 in a Benton County dairy herd.
Since the outbreak began in March 2024, HPAI has been detected in dairy cattle across 19 states. Fewer states have reported new cases in 2026, but detections continue.
A dairy worker in Yakima County who had been exposed to infected cattle also tested positive for H5N1. The worker developed eye irritation and upper respiratory symptoms but did not experience severe illness or require hospitalization, according to the Centers for Disease Control and Prevention (CDC).
H5N1 has also been detected in dairy herds in Texas and Kansas in recent weeks. USDA data from late October showed four affected herds in Texas and one in Kansas during the preceding 30 days.
More Dairy Herds Test Positive
Washington’s H5N1 outbreak has grown quickly since the first two dairy herds tested positive Oct. 8. Six more herds tested positive over the following week, and a ninth case was confirmed Oct. 26, showing the virus continues to spread as state officials work with dairy farmers to contain it.
The latest infected herd was identified through routine surveillance by the Washington Animal Disease Diagnostic Laboratory before cows showed signs of illness.
“Seeing the virus move to another county is disappointing but our dairy farmers are working hard to implement their biosecurity plans, share lessons learned and help each other get through this,” says Washington State Veterinarian Amber Itle, VMD, MS.
Itle says early detection gives dairy farmers and veterinarians more opportunity to respond before the virus spreads further.
“This isn’t new for the country, but it is new for Washington. I’ve been in awe of how hard our veterinarians and dairy farmers work together every day to keep their cows healthy, keep their workers safe and keep operating despite all the uncertainty this virus brings with it,” she says.
Washington officials hope routine surveillance and on-farm prevention measures will help limit transmission within and between dairy and poultry facilities.
Human Case Confirmed in Dairy Employee
The Washington State Department of Health has also reported a confirmed human case of avian influenza on Oct. 15. The individual was a dairy employee who had been exposed to infected cattle in Yakima County.
According to the CDC’s week 41 influenza surveillance report, the adult worker developed eye irritation and upper respiratory symptoms. State testing initially detected an H5 virus, and subsequent testing by the Centers for Disease Control and Prevention (CDC) confirmed H5N1.
The worker did not experience severe illness or require hospitalization. Health officials are contacting people who had close contact with the employee to monitor for symptoms and provide access to testing or treatment if needed. The CDC continues to assess the risk to the general public as low, and health officials have not identified evidence of human-to-human transmission associated with this case.
Biosecurity Remains a Priority
As HPAI continues to surface in dairy herds, Farm Journal research points to areas where farms could strengthen their biosecurity practices.
Research presented at the 2025 MILK Business Conference found that 68% of surveyed dairy farms with at least 250 cows had a biosecurity plan. But more than one-third, 34%, said they did not review their plans regularly.
The survey also found gaps in controlling access to farm facilities. More than 20% of surveyed dairies did not secure access to barns, while 38% did not restrict access to feed-storage areas. Sixteen percent did not monitor visitor access, and 33% used camera surveillance to oversee their facilities.
The findings suggest that having a written plan does not always mean every potential route for disease transmission is being addressed. Visitor policies, access to livestock and feed areas, and the movement of people and equipment between farms are all worth reviewing.
Kirk Ramsey, a professional services veterinarian with Neogen who reviewed the survey results, says biosecurity practices need to carry through to daily farm routines.
“We need biosecurity efforts to be more impactful at the ground level. Not only to prevent major outbreaks, but to even protect employees and families from the things being taken home every day,” Ramsey says.
Producers can use the findings as a starting point for reviewing their own protocols with employees and veterinarians. That includes checking who can enter barns and feed-storage areas, how visitor access is tracked and whether equipment and footwear are cleaned before moving between animal areas.
