Bird flu has made an unwelcome return to the Beehive State’s dairy industry.

The Utah Department of Agriculture and Food said Tuesday that a milk sample from a Cache County dairy tested positive for highly pathogenic avian influenza, the first detection in Utah cattle since early last year.

The positive test result came back Monday afternoon after the northern Utah dairy grew “suspicious” that its herd had contracted bird flu, State Veterinarian Amanda Price said.

“They had a bunch of cattle with fevers,” Price said, “that went off feed, they had decreased milk production.”

The state’s milk supply, however, is not expected to be affected, Price said. That’s because pasteurization kills the virus, allowing the dairy to continue shipping milk to its processor, she said.

To quell any further spread of the virus, state agriculture officials said in a news release that all dairy farms in Cache County will undergo weekly surveillance testing.

The state did not name the facility with the positive case.

Any dairy where bird flu is detected will be placed under quarantine, preventing cattle from being moved on or off the property, according to the news release. The only exception is for cows “going directly to slaughter,” the agriculture department said.

A quarantined dairy can resume normal operations after returning two consecutive weeks of negative bulk tank milk tests, Price said.

The last outbreak in Utah unfolded in October 2024, when bird flu was first detected in a commercial poultry flock in Cache County. Nearly 2 million chickens were culled to contain the virus, which had eventually spread to eight commercial dairies in Cache Valley.

Though the illness is often fatal to domestic poultry like chickens and turkeys, Price said cattle tend to recover from the virus.

Still, Price said increased monitoring is critical because some Cache Valley herds exposed during the 2024 outbreak may still carry antibodies, potentially masking signs of infection and making new cases harder to detect.

Price, however, said how the virus moves from dairy to dairy remains unclear.

“We haven’t found the smoking gun that moves it from dairy to dairy,” Price said. “It could be movement of vehicles, movement of people. Rodents could move it, flies could move it.”

One concern, she said, is the risk of the virus spreading to poultry operations, where outbreaks can be far more devastating.

“Then we do have to go in and depopulate those birds, and so we want to do everything that we can to limit it to the dairies,” Price said.

Price said the virus does not currently pose an immediate public health threat, and said no major disruptions to the food supply are expected. Utah has not recorded a confirmed human case of bird flu, she said.

The agriculture department said producers should report any signs of illness in poultry or cattle to the state veterinarian’s office at statevet@utah.gov.