Oregon confirms its first bird-flu infection in a dairy herd
The USDA’s National Veterinary Services Laboratories used polymerase chain reaction (PCR) testing to confirm HPAI H5 clade 2.3.4.4b in the affected herd. APHIS will carry out genetic sequencing and release its final findings when they become available. Earlier tests on the herd had repeatedly returned negative results. Its testing formed part of Oregon’s continuing dairy-cattle surveillance under the National Milk Testing Strategy.
Since the outbreak started in March 2024, infections have been recorded in dairy cattle across 22 states. During 2026, APHIS has identified infections in states that had previously been unaffected. The agency and the Oregon Department of Agriculture are conducting further investigations on farms, carrying out diagnostic tests and gathering epidemiological information. Their work is intended to clarify the detection and help prevent the virus from spreading further.
USDA’s strategy for eradicating HPAI remains unchanged following the Oregon finding. APHIS identifies biosecurity as central to reducing the risk of introducing the disease onto farms or transmitting it between premises. The agency advises every dairy farm to strengthen its biosecurity measures, alongside the continuing surveillance and investigation work.
Producers are urged to notify their state veterinarian immediately if livestock develop clinical signs of illness. The reporting advice also covers unusual instances of sick or dead wildlife. These recommendations accompany the agency’s call for enhanced precautions across dairy farms, rather than being limited to the herd where the virus was detected.
The US Food and Drug Administration says it remains confident that pasteurisation inactivates the HPAI virus and that commercially available pasteurised milk is safe. Dairy operations must supply processors with milk from healthy animals only when it is intended for human consumption. Milk produced by affected animals is being kept out of commercial milk tanks or destroyed.
The US Centers for Disease Control and Prevention (CDC) assesses the risk to the wider public from HPAI viruses circulating among birds and American dairy cattle as low. People whose work or recreational activities bring them into contact with infected birds or mammals face a higher infection risk, according to the agency. CDC advises those with such exposure to follow the precautions set out in its guidance.
