The U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed 15 additional cases of highly pathogenic avian influenza (H5N1) in dairy cattle in Idaho, marking the latest development in a growing outbreak centered in the southern region of the state.
With the latest detections, Idaho has now recorded 86 confirmed cases since March, second only to California. Nationwide, the total number of confirmed H5N1 cases in dairy cattle has reached 1,047 across 17 states.
The Idaho State Department of Agriculture (ISDA) reports that 59 herds are currently under quarantine across four counties: Gooding (34), Jerome (17), Twin Falls (7), and Cassia (1). These counties are located in close proximity in the state’s south-central dairy region.
As the third-largest milk-producing state in the country, Idaho is home to more than 350 family-owned dairy farms. The outbreak has raised concerns about economic losses due to reduced milk production in infected herds. Infected cattle typically display symptoms such as lower milk output, thickened or colostrum-like milk, changes in appetite and manure consistency, and low-grade fever.
The virus is believed to spread through a combination of factors, including direct cow-to-cow contact, contaminated equipment or clothing, environmental exposure, and potentially through infected wild birds.
The ISDA is coordinating with producers and veterinarians to implement quarantine measures and conduct herd surveillance. Affected cattle are being isolated, and producers are advised to strengthen biosecurity protocols, monitor animals closely for symptoms, and isolate newly introduced livestock for several weeks.
Despite the outbreak, public health officials continue to assure consumers that the commercial milk supply remains safe. Milk from affected cows is being discarded, and the pasteurization process effectively neutralizes the H5N1 virus. However, the safety of consuming unpasteurized milk from infected cows is not yet fully understood, and consumers are encouraged to consult with raw milk producers.
ISDA’s response follows established disease containment procedures, with efforts focused on supporting producers while minimizing animal health and production impacts. Lactating cattle at confirmed sites are monitored under quarantine, and testing strategies are tailored to each facility.
The agency also maintains an online livestock screening tool to help veterinarians and producers report suspected cases and determine if further state-level assistance is necessary.
As investigations and containment efforts continue, Idaho remains a key focus in the federal and state response to the evolving H5N1 outbreak among U.S. dairy cattle.
