Wisconsin agriculture officials confirmed the state’s first positive test of highly pathogenic avian influenza (H5N1) in a dairy herd, ending months of clean results under the National Milk Testing Strategy.
Officials with the Department of Agriculture, Trade and Consumer Protection (DATCP) said the positive sample was first identified by the Wisconsin Veterinary Diagnostic Laboratory (WVDL) on December 11 and confirmed December 12 by the National Veterinary Services Laboratory. The finding came after more than 24,000 milk samples statewide had previously tested negative since routine testing began in May.
DATCP Secretary Randy Romanski noted that Wisconsin achieved “gold” or unaffected status under the national testing program in September, reflecting months of negative results across nearly all of the state’s 5,000 dairy farms. “Avian influenza was not detected in any of those PCR tests,” Romanski said. “This is the first instance of that happening in the state of Wisconsin.”
Adam Brock, administrator of DATCP’s Division of Food and Recreational Safety, said the affected dairy had been tested five times since May, with all earlier samples—including the most recent on October 16—returning negative results. Both of last week’s samples were confirmed positive for high-path avian influenza. The farm’s field representative and processor have been notified and are following biosecurity protocols.
Brock emphasized that pasteurized milk and dairy products remain safe. “Pasteurization works for milk and dairy products,” he said.
Following the initial positive, DATCP’s Division of Animal Health contacted the farm and issued a quarantine to halt cattle movement off the operation. Dr. Angie Konkel, who leads the state’s animal health division, said early information shows no recent animal introductions onto the farm and no significant increase in cow sickness or death. “The farmer did not have a reason to suspect highly pathogenic avian influenza on the farm,” she said.
Konkel said the agency, with USDA support, is assisting the farm in reviewing and strengthening biosecurity measures. Any non-lactating cattle requiring movement will need state approval. DATCP has also alerted the Wisconsin Department of Health Services so farm employees can be monitored for flu-like symptoms as a precaution.
Further laboratory sequencing is underway to determine the specific strain and possible introduction pathway. USDA has indicated that sequencing results should be available early this week.
Romanski said the state will continue monthly participation in the National Milk Testing Strategy while consulting with USDA on next steps. He stressed that biosecurity remains critical across all livestock sectors. “Wisconsin is committed to protecting its dairy farms, its dairy workers, its dairy farmers from high-path avian influenza and other animal diseases,” he said.
DATCP and USDA have both released public statements on the case, and additional updates will be provided as the investigation develops.