A version of the H5N1 bird flu virus known as B3.13 was confirmed in March after being introduced to cattle in late 2023, scientists said. It has infected more than 950 herds in 16 states. The new version, known as D1.1, was confirmed in Nevada cattle on Friday, according to USDA. It was detected in milk collected as part of a surveillance program launched in December.
"Now we know why it's really important to test and continue testing," said Angela Rasmussen, a virus expert at the University of Saskatchewan in Canada, who helped identify the first spillover.
The D1.1 version of the virus was the type linked to the first U.S. death tied to bird flu and a severe illness in Canada. A person in Louisiana died in January after developing severe respiratory symptoms following contact with wild and backyard birds. In British Columbia, a teen girl was hospitalized for months with a virus traced to poultry.