The variant of bird flu that killed a Louisiana resident has now been found in dairy cows. Until now, the human cases of bird flu traced to cattle have been mild, mostly eye infections.
But the U.S. Department of Agriculture confirmed that a strain previously found only in wild birds has turned up in dairy herds in Nevada ‒ raising concerns that future human infections could be more serious.
Bird flu has triggered a nationwide egg shortage and price hikes in recent months, as infected chickens had to be put to death. It has also coursed through dairy farms in 16 states since last March, according to the USDA, reducing milk production. More than 60 farmworkers on both dairy and poultry farms have been infected since then, all of whom recovered.
But one Louisiana resident died last month after contracting bird flu from a backyard flock. That person, who was older and chronically ill, but not otherwise identified, was infected with the D.1.1 variant now seen in the Nevada cows. A Canadian teenager hospitalized with bird flu in November was also infected with D.1.1.
D.1.1 is common among the starlings that migrate through Nevada in the winter and might have carried the virus into the state, the Nevada Department of Agriculture said in a social media post.
The USDA said it is working with the state department of agriculture to investigate the Nevada outbreak and limit its spread.
Until last week, all bird flu in dairy herds had been identified as the B3.13 variant, which was believed to have come from wild birds in late 2023 or early 2024.
Should humans be worried about the H5N1 variant being found in dairy cattle?
The USDA confirmed the virus’s existence in the Nevada dairy cattle through milk sampling, the agency said.
The Nevada Department of Agriculture said the affected cattle, which are located in Churchill County, have been quarantined while they undergo mandatory testing at regular intervals “until the herds are confirmed to be virus-free.” The first detection of the bird flu in dairy cattle in Nevada was confirmed in Nye County in December, the state government department said.
“Ensuring the safety of the industry is our utmost priority, and the NDA is working with industry members,” Nevada agriculture department State Veterinarian Peter Rolfe said in a news release. “It is critical that animal health biosecurity practices are enhanced to help prevent the spread of disease and protect animal and worker safety.”
The state said the risk of someone catching the virus from cows is “low,” and that pasteurized dairy and well-cooked meat products are safe to consume. The USDA has determined that pasteurized milk will not transmit this H5N1 virus to humans. Raw milk sales are legal in Nevada, but there are no farms certified to sell it, according to the department.
“As always, we recommend following food safety guidelines, only eating or drinking pasteurized milk and cheeses, and cooking meat to the appropriate minimum internal temperatures,” Rolfe said.
The spread of bird flu among poultry flocks is expected to lead to further egg price increases of about 20% within the year, according to USDA. The average price per dozen was $4.10 at the end of 2024, according to the Bureau of Labor Statistics. That is twice as high as it was in August 2023.
Livestock owners encouraged to monitor their animals
The Nevada department of agriculture is encouraging livestock owners to monitor their animals for signs of illness to prevent further spread of bird flu, also called H5N1.
Cows infected with bird flu typically suffer mild symptoms, including reduced milk production, decreased appetite and coughing and sneezing, according to the department. If an animal shows signs of illness ‒ which could also include fever, eye redness or irritation, or respiratory symptoms ‒ its owner should contact their local veterinarian, the state department said.
European birds to blame for H5N1 virus spread to dairy cattle?
The culprit behind the spread of the virus could be non-native European starling populations, a species that was first introduced to New York City in 1890, the Nevada Department of Wildlife said in a Facebook post last March. These birds, which have a population of around 200 million, migrate through northern Nevada in the winter as they fly to warmer temperatures, the department said.
“European Starlings are aggressive and tend to out-compete native birds for their nesting sites, as well as can spread disease to livestock,” according to the Facebook post. “The Starling remains an unprotected bird species and are managed through USDA and wildlife nuisance control.”
Federal and state groups are in the process of removing the European starling populations in Churchill, Pershing and Lyon counties, the post said, calling their removal a “critical step” due to their ability to spread disease and contaminate animals’ food and water sources.
“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,” Nevada agriculture department Director J.J. Goicoechea said in a Jan. 31 statement. “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.”
