Bird flu in US dairy cows Bird flu, a highly pathogenic virus known as H5N1 , had been silently circulating among dairy cows in the United States for at least four months before scientists and government regulators confirmed its presence. A new analysis of genomic data by scientists at the US Department of Agriculture's Animal Disease Center reveals this disturbing reality. This study, posted on the BioRXIV server as a preprint, reveals that the H5N1 virus likely moved from wild birds to cows between mid-November and mid-January, meaning it was active in the dairy industry long before it was identified. Additionally, infected cows were found with no apparent connections, suggesting that the extent of the outbreak could be much larger than has been documented so far. Official confirmation of the presence of the virus in dairy cows occurred on March 25 in Texas. Since then, at least three dozen infected herds have been recorded in nine states. Alarmingly, at least one farm worker