A recent federal report reveals a concerning discovery: veterinarians have tested positive for past bird flu infections, despite never experiencing symptoms or realizing they were exposed. This raises the possibility of undetected bird flu cases in both humans and animals across more states than currently recognized.
The Centers for Disease Control and Prevention (CDC) conducted a study in September 2024, collecting blood samples from 150 veterinarians specializing in dairy cattle. Researchers analyzed the samples for bird flu antibodies, indicators of past infection, and inquired about the veterinarians' recent animal exposures. At the time of the study, bird flu had been confirmed in dairy cattle across 14 states, with four associated human cases in three states.
Three of the participating veterinarians showed evidence of prior bird flu infection through the presence of antibodies. Surprisingly, none had reported any flu-like symptoms or sought influenza testing since January 2024. All three worked with various animals, including dairy cattle, with some also handling non-dairy cattle, poultry, or working at livestock markets. Although one veterinarian had worked with infected poultry, none had knowingly worked with bird flu-positive dairy cattle.
While all three reported using gloves or protective clothing when handling cattle, none consistently used eye or respiratory protection. Notably, one veterinarian practiced exclusively in Georgia and South Carolina, states without any reported bird flu cases in cattle or humans.
This discovery suggests potential undetected bird flu infections in dairy cattle in states where the virus hasn't been officially identified. It underscores the critical need for swift identification of infected cattle through herd and bulk milk testing, as recently emphasized by the USDA. The asymptomatic nature of these infections also highlights the potential underestimation of human cases when relying solely on surveillance of symptomatic individuals.
The CDC stresses the importance of raising awareness about their latest recommendations, which include offering post-exposure preventive medication and testing to even asymptomatic workers who may have been exposed. This report comes as the USDA recently announced the discovery of a second type of bird flu (D1.1) in dairy cows, a strain previously only found in wild birds and poultry, suggesting a recent jump to cattle.
