More Americans could be unknowingly carrying bird flu, according to a new report from the Centers for Disease Control and Prevention. The report follows a series of random tests of 150 veterinarians,

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.

Three U.S. dairy veterinarians unknowingly had H5N1 infections, otherwise known as bird flu. This included one person who worked only in states without known outbreaks in cows, according to a new study from the U.