Signs of recent bird flu infection were found in three US veterinarians, two of whom had no known prior exposure, researchers said, suggesting potentially wider spread of the dangerous virus than has been suspected.

Highly pathogenic avian influenza (HPAI) has entered a concerning new phase, demonstrating its adaptability by spreading from birds to dairy cows. This marks the second recorded spillover of HPAI into dairy herds,

A new study shows that bird flu has silently spread from animals to some veterinarians. The study published Thursday by the Centers for Disease Control and Prevention echoes two smaller ones that detected evidence of infection in previously undiagnosed farmworkers.