DALLAS — Milk from dairy cows in Texas and Kansas has tested positive for bird flu, U.S. officials said Monday.
Officials with the Texas Animal Health Commission have confirmed that the flu virus is the type A H5N1 strain, which has been known for decades to cause outbreaks in birds and occasionally infect humans. The virus affects older dairy cows in these states and in New Mexico, causing reduced lactation and poor appetite.
It comes a week after officials in Minnesota announced that goats on a farm where there was an outbreak of bird flu among poultry had been diagnosed with the virus. This is believed to be the first time bird flu — also known as highly pathogenic avian influenza — has been detected in American livestock.
The commercial supply of milk is safe and the risk to humans is low, according to the USDA. Dairies are required to allow only milk from healthy animals into the food supply, and milk from sick animals is diverted or destroyed. Pasteurization also kills viruses and other bacteria, and the process is required for milk sold through interstate commerce, the agency said.
“At this time, there are no concerns about the safety of the commercial milk supply or that this circumstance poses a health risk to consumers,” the USDA said in a statement.
The federal government said its tests on cattle had not found any changes to the virus that would make it easier to spread to humans.
Texas dairy farmers first became alarmed three weeks ago when cattle began falling ill with what officials called a “mysterious dairy cow disease,” said Sid Miller, commissioner of the Texas Department of Agriculture. Milk production dropped sharply and the cows were lethargic and did not eat much.
“We hadn’t seen anything like this before,” he said. “Like they had a cold.”
The state Commission of Animal Health has launched an investigation that includes testing for bird flu, spokeswoman Erin Robinson said. Based on findings from Texas, USDA officials believe the cows got the virus from infected wild birds.
Experts say the animals seem to recover on their own within seven to 10 days. This is different from bird flu outbreaks in poultry, which require culling flocks to get rid of the virus. Since 2022, outbreaks have resulted in the loss of about 80 million birds in commercial flocks in the United States.
So far, the virus appears to be infecting about 10 percent of lactating dairy cows in affected herds, said Michael Payne, a veterinarian and biosecurity expert at the University of California-Davis Western Institute for Food Safety and Security.
“This is not like the highly prevalent flu in bird flocks,” he said.
Avian influenza was detected in unpasteurized, clinical samples of milk from sick cattle collected from two dairy farms in Kansas and one in Texas. The virus was also found in a nose and throat swab from another dairy in Texas.
Officials called it a fast-moving situation. The Food and Drug Administration and the Centers for Disease Control and Prevention are involved, along with officials in the three states. Another dairy-heavy state, Iowa, said it was monitoring the situation.
Dairy industry officials said producers have begun increased biosecurity efforts on U.S. farms, including restricting traffic on and off properties and limiting visits by employees and essential personnel.
Bird flu had previously been reported in 48 different mammal species, Payne noted, adding, “It was probably only a matter of time before bird flu reached ruminants.”