December 14, 2025 - 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) and ELISA (Enzyme-Linked Immunosorbent Assay) assay a detection of highly pathogenic avian influenza (HPAI) H5 clade 2.3.4.4b in a dairy cattle herd in Wisconsin. APHIS will complete genetic sequencing and announce final results as soon as they are available. This confirmation was a result of routine National Milk Testing Strategy testing, not pre-movement surveillance.

This marks the first known case of HPAI in cattle in Wisconsin. While dairy cattle in a total of 18 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 Wisconsin Department of Agriculture, Trade, and Consumer Protection to conduct additional on-farm investigations, diagnostic testing, and epidemiological data collection to better understand the detection and prevent further disease spread.