Avian influenza confirmed in dairy cattle in Washington for the first time

Highly pathogenic avian influenza (HPAI) has been confirmed in dairy cattle in Washington. These are the state’s first confirmed cases of the virus in livestock, according to an October 8 announcement from federal officials.¹

The US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) said its National Veterinary Services Laboratories identified HPAI H5 clade 2.3.4.4b in 2 herds using polymerase chain reaction (PCR) testing. Genetic sequencing is still in progress, and APHIS said it will share final results when they become available.¹

Clinical signs prompted testing

Both herds were tested after cattle showed signs consistent with avian influenza. Before then, the herds had repeatedly tested negative through routine surveillance under the National Milk Testing Strategy.¹

APHIS is working with the Washington State Department of Agriculture on additional on-farm investigations, diagnostic testing, and epidemiologic data collection to learn more about the detections and help prevent further spread.¹

Since the dairy cattle outbreak began in March 2024, infections have been reported in 19 states. APHIS noted that only a small number of states have reported cases this year.¹

Eradication strategy unchanged

According to APHIS, the Washington detections do not change USDA’s eradication strategy for HPAI in livestock. The agency continues to identify biosecurity as central to reducing the risk of the virus being introduced to a farm or spreading between premises, and it recommends enhanced biosecurity measures for all dairy operations.¹

APHIS’s biosecurity recommendations for dairy producers include²:

• Allowing only people who need to be on the farm, keeping a record of visitors, and using a single entrance and exit
• Disinfecting vehicles as they enter and leave the farm
• Cleaning and disinfecting equipment daily and avoiding borrowed tools
• Wearing dedicated boots and coveralls around the herd
• Keeping pets, other animals, wild birds, and pests such as rodents away from cattle and livestock areas
• Isolating new, borrowed, or returning animals
• Isolating sick animals and reporting them to a veterinarian or to state or federal animal health officials

The release asks producers to report livestock with clinical signs, as well as any unusual illness or deaths among wildlife, to their state veterinarian immediately.¹

Financial assistance is available to help producers strengthen biosecurity and offset HPAI-related costs.¹ Depending on whether a herd is affected, USDA support can cover biosecurity planning and costs tied to influenza A testing, veterinary care, personal protective equipment (PPE), milk disposal, and milk losses. APHIS notes that its biosecurity planning support includes enhanced measures for people who move frequently between dairy premises, such as veterinarians, milk haulers, feed truck drivers, and artificial insemination technicians. Producers can enroll through their Area Veterinarian in Charge or state animal health official.³

Milk supply and risk to people

APHIS said the detections do not affect the safety of the commercial milk supply or pose a risk to consumers. The FDA is confident that pasteurization inactivates HPAI virus. Dairies are required to send only milk from healthy animals into processing for human consumption, and milk from affected animals is being diverted or destroyed so it does not enter the food supply.¹

The Centers for Disease Control and Prevention (CDC) considers the risk to the general public from HPAI viruses circulating in US birds and dairy cattle to be low. However, people with occupational or recreational exposure to infected birds or mammals face a higher risk of infection and should follow CDC precautions.¹

CDC’s interim guidance for employers, last updated May 2025, identifies poultry and dairy workers as the most likely to be exposed. It also lists veterinarians and veterinary staff among other workers who may be at risk. According to the guidance, people can become infected when enough virus gets into the eyes, nose, or mouth or is inhaled. The highest exposure level covers contact with live or dead animals that are confirmed or potentially infected, and contact with raw milk, udders, or other secretions from a farm with such animals. For those tasks, CDC recommends a combination of engineering controls, administrative controls, and high-exposure PPE.⁴

References

1. USDA confirms highly pathogenic avian influenza in two dairy herds in Washington. News release. US Department of Agriculture Animal and Plant Health Inspection Service. October 8, 2026. Accessed October 9, 2026. https://www.aphis.usda.gov/news/agency-announcements/usda-confirms-highly-pathogenic-avian-influenza-two-dairy-herds
2. Enhance biosecurity. US Department of Agriculture Animal and Plant Health Inspection Service. Updated February 6, 2026. Accessed October 9, 2026. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock/enhance-biosecurity
3. Financial assistance. US Department of Agriculture Animal and Plant Health Inspection Service. Updated May 31, 2026. Accessed October 9, 2026. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock/financial-assistance
4. Reducing exposure for workers to avian influenza A viruses. Centers for Disease Control and Prevention. May 6, 2025. Accessed October 9, 2026. https://www.cdc.gov/bird-flu/worker-safety/index.html