A new strain of the H5N1 bird flu virus, D1.1, has been detected in six dairy herds in Nevada, marking a significant shift in the nation’s efforts to contain the virus. The strain is not the same as B3.13, which has been circulating in other US dairy farms.
Experts say that introducing avian flu into cattle herds by birds is a turning point, making it easier to control the spread of the virus within cow-to-cow transmission rather than bird-to-cow transmission. This new strain has been linked to severe human infections, including hospitalizations and deaths.
According to Dr. Scott Hensley, a microbiologist, “It’s much easier to control virus spread when you’re talking about a virus spreading from cow to cow.” The affected dairy farms have provided contact information for their workers who are being monitored for signs of infection, and they are being offered personal protective equipment.
Notably, the D1.1 infections in cows appear to be similar in severity to B3.13 infections, with symptoms such as reduced appetite and milk production. Most recover with veterinary care.
The detection was made through a US Department of Agriculture program testing milk in large silos across the US. This finding raises critical questions about how dairy cattle are being exposed to the virus and whether it’s possible to contain the H5N1 outbreak, which has been detected in 957 herds in 16 states since March 2024.
As the situation continues to unfold, scientists are studying the D1.1 strain to learn more about its capabilities and how it appears to be spreading aggressively.
Source: https://edition.cnn.com/2025/02/05/health/bird-flu-cattle-nevada/index.html