October 8, 2026-Today, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) National Veterinary Services Laboratories (NVSL) confirmed via PCR (polymerase chain reaction) detection of highly pathogenic avian influenza (HPAI) H5 clade 2.3.4.4b in two dairy cattle herds in Washington. APHIS will complete genetic sequencing and announce final results as soon as they are available. The affected herds were tested after exhibiting clinical signs consistent with avian influenza. Prior to this detection, the herds consistently tested negative through routine surveillance conducted under the National Milk Testing Strategy program.

These are the first confirmed case detections of HPAI in livestock in the State of Washington. While dairy cattle in a total of 19 states have been infected since the start of the outbreak in March 2024, APHIS has seen cases in only a small number of states this year. APHIS is working closely with the Washington Department of Agriculture to conduct additional on-farm investigations, diagnostic testing, and epidemiological data collection to better understand the detection and prevent further disease spread.