A variant of bird flu, previously found only in wild birds, has now been detected in six dairy herds in Nevada, raising concerns that the virus may be here to stay.
The new strain, D1.1, is different from B3.13, the version that has been making rounds across the United States.
This is the first time the D1.1 strain has been detected in dairy cattle, indicating that the animals contracted the virus from wild birds rather than other cows. This marks the second known instance of bird flu being transmitted to cattle herds by wild birds.
This suggests that the H5N1 virus is continously circulating in North America and that it may eventually pass onto humans.
Dr. Louise Moncla, a pathobiologist who runs a lab that studies the emergence of viruses in human populations, believes ‘it should be classified as an endemic virus’.
Dr. Eric Deeble who works for the US Department of Agriculture, said officials were ‘confident’ that they would be able to eliminate H5N1 from national herds.
Repeated infections of cattle via wild birds, however, will make that less likely.
Dr. Scott Hensley, a microbiologist at the University of Pennslyvania, said it’s much easier to control the spread of a virus when it’s only spreading from cow to cow’ versus birds to cow.
With the bird flu outbreak,millions of birds have been culled, causing price hikes and a national egg shortage. Since last year, the virus has also appeared in numerous dairy farms across 16 states.
Over 60 farmworkers were also infected with the bird flu, though they have all since recovered.
New Strain Can Cause Severe Disease In Humans
The new strain, D1.1, is linked to severe infections in humans. Last fall, a teenager in British Columbia was hospitalized after becoming infected. They remained in critical condition for several days before eventually recovering.
In January, a senior in Louisiana also became infected with the strain; they later died from the infection.
Scientists are currently studying the new strain to find out how it’s able to ‘spread so aggressively’.
Dr. J.J. Goicoechea, who leads the Nevada Department of Agriculture, said the D1.1 strain was originally found in August 2024. The affected dairy farms have since provided officials with their workers’ information who are actively being monitored for signs of infection.
In cows, however, D1.1 does not appear to cause more severe infections compared to the B3.13 strain.
Goicoechea said cows infected with D1.1 exhibit the same clinical signs, which include a loss of appetite and drop in milk production. With veterinary care, most recover without issues.
The emergence of the new strain raises important questions about how dairy cattle are being exposed to the virus and whether or not we’ll be able to contain it, which is spreading quickly among birds and other animals.
However, health officials say the risk to people remains low.
