First human case of avian flu transmitted by dairy cows detected

Migratory waterfowl are to blame for growing outbreaks of bird flu in Texas cows and poultry, and wild birds carrying the virus should head north soon, state Agriculture Commissioner Sid Miller said.

The US government has reported cases of the disease in seven dairy herds in Texas and a person who had contact with cows, making it the state most affected by the first outbreaks in cattle in the country. Texas is the largest livestock producer in the United States.

The cases in dairy cattle and the second human case in two years in the United States renewed concerns about the virus, which has been infecting flocks of poultry and a growing number of other species around the world since 2022.

A positive test at a Texas egg farm led egg producer Cal-Maine (CALM.O) to slaughter 1.6 million laying hens, the company said. Texas has never before experienced such a major outbreak at a commercial poultry facility, Miller said.

“This is transmitted by waterfowl,” he said in an interview. “We are ready for the ducks to head north to their nesting areas.”

The United States Department of Agriculture (USDA) reported for the first time that a cow and milk from two Texas dairies tested positive for bird flu, along with milk from two Kansas dairies. The agency later confirmed cases in additional dairy herds in Texas, New Mexico, Michigan and Idaho.

The virus strain found in later states is very similar to the strain confirmed in the initial cases in Texas and Kansas that appear to have been introduced by wild birds, the USDA said.

Experts said feces or other materials from infected wild birds could have contaminated food or water supplies ingested by cows at dairies, although that has not been confirmed.

The USDA said it could not rule out transmission of the disease among livestock. In Michigan, the flock dairyman who tested positive had recently received cows from Texasaccording to the agency.

Following the outbreaks, Mexico, a major market for U.S. beef and dairy products, said it is increasing surveillance and beefing up inspections of U.S. livestock imports.

bird flu It has primarily affected older cows in infected dairies, and “only a small portion of each herd exhibits clinical signs,” the USDA said in an email. The agency added that it has not received reports of cattle showing clinical signs of illness or samples of cattle for testing for bird flu.

Why dairy cattle and not beef cattle? “Everyone is scratching their heads,” said Michael Kleinhenz, a veterinarian and associate clinical professor of dairy cattle health at Texas A&M University.

“Here in the Texas panhandle, we have dairies next to feedlots and cows very close in the field, and we're only seeing it in the dairies.”


The US Centers for Disease Control and Prevention considers the risk of bird flu to humans to be low. The Texas patient's only symptom was eye inflammation, according to the state health department.

President Joe Biden has been briefed on the bird flu situation, White House spokeswoman Karine Jean-Pierre told reporters at a news briefing.

Richard Webby, a virologist at St. Jude Children's Research Hospital in Memphis, said flu testing in livestock is not routine and it was important to make the connection between the disease in cows, ducks and cats on farms.

Some smart people made the link and actually tested them for flu,” said Webby, director of the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds.

The Texas outbreak may have started when a mysterious disease affected about 40% of the state's dairy herds, Miller said. He said he suspects it was bird flu, although authorities did not know this at the time and cannot confirm it because the animals recovered.

“We were analyzing all the livestock diseases we could think of and then someone said: 'What are all these dead birds doing in the dairies?'”Miller said.

(With information from Reuters)