U.S. dairy cattle tested positive for a strain of bird flu that previously had not been seen in cows, the U.S. Department of Agriculture said on Wednesday, ramping up concerns about the persistent spread of the virus.

On Jan. 31, 2025, the USDA Animal and Plant Health Inspection Service (APHIS) National Veterinary Services Laboratories (NVSL) confirmed by whole genome sequence the first detection of highly pathogenic avian influenza (HPAI) H5N1 clade 2.

The USDA said four Nevada dairy herds were infected with an H5N1 bird flu strain that has circulated in wild birds, making prospects for containment in cows appear dim.

The U.S. Department of Agriculture said Wednesday that a second type of H5N1 bird flu had infected U.S. dairy herds, suggesting that cattle are more susceptible to the avian virus than previously believed and putting dairy workers at greater risk.

Experts said the discovery raises questions about how widely the virus has spread, and underscores the difficulty of controlling infections among animals and people working with them. View on euronews