Three dairy veterinarians, including one who worked only in states with no known bird flu outbreaks in cows, had recent, undetected bird flu infections, according to a new study from the Centers for Disease Control and Prevention. The results are based on antibody testing of 150 veterinarians working in 46 U.S. states.

A new report suggests that more Americans may be walking around with bird flu − and not even know it. Researchers from the Centers for Disease Control and Prevention randomly tested 150 veterinarians for H5N1,

CDC finds H5 bird flu antibodies in 3 veterinary practitioners, highlighting need for enhanced surveillance and safety protocols.

The new study is more evidence that the official U.S. tally of confirmed human bird flu infections—68 in the last year—is likely a significant undercount.

Bird flu infections were detected among cattle veterinarians tested last fall, including two people with no known exposure to animals with the virus, according to a report released by the U.S. Centers for Disease Control and Prevention on Thursday.