The U.S. Department of Agriculture and the Centers for Disease Control and Prevention issued a joint advisory on Thursday urging dairy farm workers in Cache County, Utah, to undergo voluntary health screening following confirmation that a local dairy herd has tested positive for highly pathogenic avian influenza (HPAI) H5N1. The announcement marks the latest outbreak in the ongoing wave of HPAI cases that has spread through U.S. dairy herds since 2024.

The advisory instructs farm employees who have had close contact with affected cattle or raw milk to report any flu-like symptoms — including conjunctivitis, fever, and respiratory distress — to county health officials. Utah's Bureau of Epidemiology confirmed it is coordinating with Cache County public health authorities to set up a mobile screening station near the affected facility, with antiviral stockpiles of oseltamivir pre-positioned as a precautionary measure.

The Utah Department of Agriculture and Food said Thursday that it has expanded bulk raw milk testing across Cache County's dairy operations, asking producers to submit twice-weekly samples to state veterinary laboratories. Officials emphasised that commercially pasteurised milk remains safe and that no human infections have been detected in connection with the Cache County farm. The FDA reiterated its longstanding advisory against consuming raw milk.

Public health experts noted that the Cache County detection is consistent with the broader national pattern, in which migratory bird corridors continue to seed new dairy exposures across western states. Dr. Eric Deeble, acting chief veterinary officer at the USDA, said the agency is conducting full genomic sequencing on the Utah strain to determine whether it is related to clades currently circulating in the Pacific Flyway. Results are expected within 48 to 72 hours.

The CDC said its overall risk assessment for the general public remains low, but stressed that farm workers represent an elevated-risk population warranting continued vigilance. The agency urged state health departments to maintain occupational health outreach efforts and reminded clinicians to consider HPAI in the differential diagnosis for any farm worker presenting with unexplained febrile illness in affected counties.