H5N1 testing in cow veterinarians suggests bird flu is spreading silently

Three veterinarians who work with cows have tested positive for prior infections of H5 bird flu, according to a study released today by the Centers for Disease Control and Prevention.

The finding may not seem surprising, given the sweeping and ongoing outbreak of H5N1 among dairy farms in the US, which has reached 968 herds in 16 states and led to infections in 41 dairy workers. However, it is notable that none of the three veterinarians were aware of being infected, and none of them worked with cows that were known or suspected to be infected with H5N1. In fact, one of them only worked in Georgia and South Carolina, two states where H5N1 infections in dairy cows and humans have never been reported.

The findings suggest that the virus may be moving in animals and people silently, and that our surveillance systems are missing infections—both long-held fears among health experts.

The authors of the study, led by researchers at the CDC, put the takeaway slightly differently, writing: “These findings suggest the possible benefit of systematic surveillance for rapid identification of HPAI A(H5) virus in dairy cattle, milk, and humans who are exposed to cattle to ensure appropriate hazard assessments.”