Bird flu has jumped to cattle for the first time in the United States and recently infected a dairy worker in Texas.

Agriculture officials in Minnesota are watching closely for infections in the state's cattle herds and dairies, while public health officials continue to say the risk to humans remains low and pasteurized milk remains safe.

"I'd be surprised if it isn't here already [in cattle]," said Dr. Joe Armstrong, a University of Minnesota Extension livestock educator.

The ongoing highly pathogenic avian influenza (HPAI) outbreak began in 2022 has resulted in the mass culling of turkeys and chickens across the state whenever an infection is found. Although evidence suggests the fast-spreading disease is not lethal in cattle, Armstrong said Tuesday federal and state officials are working with farmers and veterinarians to keep animals safe.

There are no reports of HPAI in cattle in Minnesota. Last week, dairy cows and their milk in Texas and Kansas tested positive for the virus. By Friday, a dairy herd in Michigan that had received cows from Texas also had sick cattle.

Last month, Minnesota officials reported the nation's first positive bird flu infection of a ruminant. A litter of Stevens County goat kids shared water with infected poultry and later several tested positive for the virus.

Animal health officials say livestock owners should be on the watch for symptoms. Dr. Brian Hoefs, Minnesota's state veterinarian, told the state's House Agriculture Committee Tuesday the infected Texas cattle ate less feed, showed respiratory stress and had dark, tacky manure. Evidence of HPAI was found in tests of raw milk.

"It's basically the same virus that's been circulating since 2022," Hoefs said. One distinct difference from birds, however: All the sick cows recovered.

Armstrong said veterinarians, U.S. Department of Agriculture officials and researchers may have just discovered an illness that was always present, but it is just now being detected because of heightened attention to influenza in animals.

"We're still making those connections and trying to figure that out," Armstrong said.

Low risk to humans

As bird flu is found in more mammals, concerns are growing the virus could adapt to infect humans.

On Monday, the CDC reported a human exposed to cattle in Texas had become sick with avian influenza. The person had red eyes, with symptoms resembling conjunctivitis, and was treated with an antiviral drug for the flu.

That's just the second reported human infection in the United States during the current outbreak. In 2022, an individual working with poultry in Colorado also tested positive for bird flu and recovered.

Michael Osterholm, an epidemiologist at the University of Minnesota, said evidence at this point suggests humans would need to come into close contact with the animals to be infected. Even then, people recover.

"At this point, I agree with the CDC, the risk assessment [for humans] is low," Osterholm said.

The state's agriculture leaders say those working in the industry — especially across dairy-rich central, western and southeastern Minnesota — should be observant of strange behavior in both dairy and beef cows, including lack of appetite and decreased lactation. They say horses should also be watched for unusual changes in behavior.

Moreover, farmers need to prepare laborers, many of whom are immigrants or do not speak English as a first language, to use extra precaution around animals and unpasteurized milk.

"Most of these people working in the parlor are at eye level, and they're working with raw milk," said Armstrong, who underscored calls for farm workers to wear at least goggles and masks in the barns. "I think farmers will do a good job [educating workers] because they recognize how valuable that workforce is and how much they mean to the industry in our country."

Officials said pasteurized milk remains safe to drink. The Food and Drug Administration said last week there "continues to be no concern about the safety of the interstate commercial milk supply," as cow's milk is pasteurized before going to market. Moreover, only milk from healthy animals is authorized for distribution.

The flu's devastating economic toll for Minnesota's turkey industry remains an unnerving recent memory.

Across the country, more than 79 million birds have died from the virus since 2022, according to a federal database. According to a Star Tribune analysis, the federal government paid $135 million in indemnity to Minnesota's turkey and chicken growers.

The disease is largely spread by migratory birds, often through shared water sources with domesticated animals. In 2024, the state has only seen three HPAI outbreaks, all in backyard flocks.

"It provides a new dynamic to the outbreak," said Ashley Kohls, executive director of Minnesota Turkey Growers Association. "We're not changing, per se, anything that we're doing."

Star Tribune staff writer Brooks Johnson contributed to this story.