News — A new variant of the H5N1 strain of avian influenza — commonly known as bird flu — has been detected in Nevada, first in cows and later in a dairy worker, raising concerns about the virus’s spread.
Additionally, three veterinarians specializing in cattle have tested positive for bird flu despite presenting zero symptoms. One worked in two different states without any reported infections in those areas.
The findings indicate that bird flu is more widespread than previously thought, according to Sarah Michaels, an infectious disease expert at Tulane University’s Celia Scott Weatherhead School of Public Health and Tropical Medicine.
“It will be difficult to contain,” Michaels said. “Recent screenings and the national milk testing program have shown that bird flu has spilled over from wild birds to cattle more than once. And this report of infections in three veterinarians highlights the importance of rapidly identifying infected dairy cattle, continued testing of bulk milk, and monitoring human infections among those at increased risk.”
The newly identified D1.1 variant had only previously been found in wild birds with spillover into domestic poultry. It had not previously been detected in cattle. The original B3.13 strain of bird flu was responsible for earlier infections in dairy herds that made headlines last year.
The infection of the Nevada dairy worker marks the third known human case of the D1.1 variant. In January, a Louisiana man died after contracting the variant from a backyard flock of chickens, marking the first reported human fatality. In November 2024, a Canadian teenager was hospitalized with the same strain.
Michaels said the presence of two different types of bird flu will also make it difficult to track the spread.
As of now, there have been 68 confirmed human cases of avian influenza in the U.S., four of which were detected through national flu surveillance. All but three of those cases have been linked to exposure to infected animals. There is no evidence of human-to-human transmission of the virus.
Still, Michaels urged the public to take precautions when handling sick or dead birds and certain food products.
“Eggs and meat should be cooked thoroughly, and people should refrain from drinking raw milk,” Michaels said.
The Centers for Disease Control and Prevention (CDC) has developed candidate vaccine viruses that could be used to produce bird flu vaccines if necessary. While the seasonal flu vaccine does not protect against bird flu, Michaels encouraged people to get a flu shot to guard against co-infection with seasonal and avian influenza.
The U.S. is currently experiencing a second winter wave of flu cases, the worst in 15 years, according to the CDC.
“Many cases are among children, and fewer children are getting vaccinated against the flu compared to before the COVID-19 pandemic,” Michaels said. “It’s not too late to get a flu shot, and while it won’t protect against bird flu, it does provide important protection against seasonal influenza.”
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