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.

Blood testing of large-animal veterinarians suggests that H5N1 bird flu has spread more widely than US surveillance of the virus is capturing, according to a new study by federal and state disease detectives.

Three veterinarians had antibodies to bird flu virus, which suggests recent infection, the report said. None of them knew they were working with dairy cattle with known or suspect

Bird flu infections were detected among 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.

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

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.