A recent study indicates that the H5N1 bird flu may have quietly infected veterinarians, according to findings released by the Centers for Disease Control and Prevention (CDC). This research reinforces earlier smaller studies that found asymptomatic infections among farmworkers. In those cases, some workers recalled experiencing symptoms of the virus, whereas none of the veterinarians in this latest study reported any such issues.
Dr. Gregory Gray, an infectious disease expert at the University of Texas Medical Branch in Galveston, argues that the current official count of confirmed human cases in the U.S. — which stands at 68 over the past year — likely underestimates the true number of infections. He stated that this suggests many individuals are infected through their work without showing signs of illness, leading them not to seek medical attention. Gray emphasized that understanding bird flu transmission requires looking beyond those who visit clinics with visible symptoms.
The study involved CDC researchers attending a veterinary conference hosted by the American Association of Bovine Practitioners in Columbus, Ohio, in September 2024. They gathered data from 150 veterinarians across 46 states, asking them to complete a survey and provide blood samples. Despite no one reporting symptoms like red eyes typically linked to bird flu, laboratory tests revealed that three veterinarians — about 2% of participants — had antibodies for H5N1. All three had experience working with dairy cattle and other animals, with one having had contact with an infected poultry flock.
In a separate study conducted the previous year, Gray and his colleagues discovered that among 14 dairy farmworkers surveyed, two (approximately 14%) showed signs of past infection, both of whom had experienced symptoms but weren’t officially diagnosed. Another CDC investigation involving 115 dairy workers found that 8% had recent antibody evidence; notably, half of these individuals remembered feeling ill.
Gray cautioned that these studies, while revealing, are too limited to create a definitive estimate of undiagnosed cases. Nonetheless, he suggested even a small percentage could equate to hundreds or possibly thousands of individuals in the U.S. who contracted the virus while handling animals.
Despite these findings, Jacqueline Nolting, a researcher at Ohio State University who assisted with the study, reassured that there’s no immediate cause for alarm. Research shows that people who become infected typically develop an antibody response, potentially establishing natural immunity, which she considers encouraging.
However, the situation could deteriorate if the virus undergoes mutations that make it dangerous to humans or enable it to spread easily between people, Nolting cautioned.
Currently, H5N1 is spreading among various animals, including wild birds and poultry. The heightened environmental presence increases the risk of human exposure, officials warn. Presently, CDC states that the overall risk to the general public remains low, but they continue to recommend safety measures for individuals who come into contact with sick or deceased birds, such as wearing gloves, masks, and eye protection when handling poultry.
Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, noted that there is general agreement among experts that the virus is circulating more widely than documented. He anticipates increased guidance for veterinarians on necessary protective measures to prevent infection, including the use of gloves and masks.
