A Nevada dairy worker has become the first human known to be infected with a new version of bird flu from a dairy herd.
The flu strain (D1.1), which has been circulating in wild birds, is different from the version that has been spreading in American dairy herds since last year, federal health officials said Monday. It’s also different from the strain of the virus (B3.13) that has caused the majority of human infections in the U.S.
D1.1 has a mutation that could make the virus spread more easily in mammals.
“That’s a big deal,” said Michael Osterholm, an infectious disease expert and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, reported NBC News.
Some experts fear that it could mark a new chapter in the outbreak, or that bird flu may become endemic in the U.S.,” warned Andrea Garcia, vice president of science, medicine and public health at the American Medical Association. “This is something we are continuing to very closely follow.”
The dairy worker is Nevada’s “first and only human case of avian influenza” in an adult who was exposed to infected dairy cattle while working at a dairy farm, state health officials said in a statement.
“There is currently no evidence of person to person spread of this virus,” the statement added. “While the current public health risk for the general public remains low, people who work with birds, poultry or cows ... are at higher risk,” warned health officials.
The Nevada dairy worker’s illness was considered mild, but is the latest indication of a mutating disease infecting humans.
The dairy worker’s main symptom was eye redness and irritation. The person, who was not identified, wasn't hospitalized and has recovered, according to the Centers for Disease Control and Prevention.
Close contacts of the infected dairy worker are being closely monitored.
The H5N1 strain of bird flu had been seen before in more than a dozen people exposed to poultry. But this is the first time an infection was traced to a cow that then jumped to a human. The Nevada dairy worker was exposed at a farm in Churchill County, in the west central part of the state, state health officials said.
CDC officials said there is no evidence the virus has spread from the dairy worker to anyone else.
Another version of bird flu known as B3.13 was confirmed in March after spreading to cattle in late 2023, according to scientists. It has infected 962 cattle herds in 16 states, the vast majority of them in California.
The D1.1 strain was confirmed in Nevada cattle the last day of January. It was found in milk collected as part of a monitoring program launched in December.
That discovery meant that distinct forms of the virus spread from wild birds into cattle at least twice. Experts said it raises questions about a wider spread and the difficulty of controlling infections in animals and the people who work with them.
At least 68 people in the U.S. have been reported infected with bird flu in the last year, according to CDC data. All but a small handful worked closely with cows or poultry.
Most caught the B3.13 version. The CDC previously said the D1.1 version had been seen only in cases in Louisiana and Washington state. But on Monday, the agency revealed that available data indicates D1.1 last year likely infected a total of 15 people in five states – Iowa, Louisiana, Oregon, Washington and Wisconsin – all related to poultry.
The D1.1 version of the virus was linked to the first U.S. death tied to bird flu and to a severe illness in Canada. A person in Louisiana died in January after developing severe respiratory symptoms following contact with wild and backyard birds. In British Columbia, a teen girl was hospitalized for months with a virus traced to poultry.
New York Governor Kathy Hochul has ordered a temporary closure of live-poultry markets after bird flu was detected in the outer boroughs of New York City.
The order, signed by Hochul on Friday, requires the markets to close down between February 7-14 as facilities undergo a complete disinfection process, whether the markets have had cases of bird flu or not.
The Associated Press contributed to this report.
