A Deadly Strain of Bird Flu Has Been Detected in Dairy Cows in Nevada

A new strain of H5N1, also known as avian influenza or “bird flu,” has been detected in dairy herds in Nevada.

On Friday, the U.S. Department of Agriculture (USDA) announced that it had concluded genome sequencing of milk from Nevada cows and found the D1.1 genotype for the first time. Until now, all other dairy herds that tested positive had tested for the B3.13 genotype. 

“The challenge with this virus is that it may be spread through contaminated clothing worn and equipment shared between animals, but birds carrying the disease can also infect domestic animals and livestock,” J.J. Goicoechea, the director of Nevada’s Department of Agriculture, shared in a statement released on January 31. “We cannot stress enough how important it is to keep equipment clean, practice good animal health safety practices, and bolster biosecurity measures to prevent the spread of disease.”

According to the announcement, the USDA Wildlife Services, as part of the National Milk Testing Strategy, is now surveilling dairy silos to detect the virus before dairy cows show symptoms and is also testing surrounding wildlife for the strain to “better determine which strain and how it is spreading.” This includes “removing non-native European starling populations in Churchill, Pershing, and Lyon Counties,” which are considered a “nuisance population.” 

And while the Centers for Disease Control and Prevention maintain that the risk is low for humans, the virus’s ability to jump from birds to cattle so easily is worrying experts.  

“We’re seeing the H5N1 virus itself be smarter than all of us,” Beth Thompson, South Dakota’s state veterinarian, told Reuters. “It’s modifying itself so it’s not just staying in the poultry and the wild waterfowl. It’s picking up a home in the mammals.”

This particular strain — D1.1 — is also the same strain that was associated with two severe human infections, including a teenager in British Columbia in the fall of 2024 and in the case from Louisiana, where the person died from the infection in January. 

However, Goicoechea told CNN that the cows infected with D1.1 did not appear to have more severe symptoms than those with B3.13 infections. 

“We’re seeing exactly the same clinical signs,” Goicoechea said, adding that those symptoms include the cows losing their appetite and a drop in milk supply.  “It’s very, very similar signs to what we’ve seen for really the last year since this started in Texas and Kansas.” 

Bird flu, the USDA noted, has been detected in 957 herds across 16 states since March of 2024. The bird flu, the CDC confirmed, has infected 67 humans in the U.S. to date. According to the CDC, 153,866,301 birds, including commercial poultry, have been infected with avian influenza. As Food & Wine has extensively reported, this has also severely affected the U.S. egg supply, with the cost of a dozen large Grade A eggs reaching $4.15 in December of 2024, marking a 37% increase in the price of eggs year over year. And there appears to be no end in sight.