The report is the latest evidence that the outbreak in dairy herds is spreading undetected in cows, and the spillover into people at highest risk of exposure is going unnoticed.

Some people didn’t know they had a bird flu infection, A new study shows the bird flu has silently spread from animals to some veterinarians. It echoes two smaller studies that detected evidence of infection in previously undiagnosed farmworkers.

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.