“Rub some tallow on it and drink some raw milk”

3 veterinarians had recent H5N1 infections but didn't know they had been exposed

Mary Van Beusekom, MS

In Morbidity and Mortality Weekly Report, the US Centers for Disease Control and Prevention (CDC) reports on recent avian influenza A (H5N1) infections in three veterinarians who work with cattle but didn't know they had been exposed to the virus.

The CDC's analysis of blood samples from 150 bovine veterinarians in 46 US states and Canada during the current H5N1outbreak in dairy cows and poultry revealed that three asymptomatic US practitioners (2%) had antibodies to H5N1 in September, suggesting recent infection. 

Two of them reported no exposures to infected animals, and one practiced in Georgia and South Carolina, which have had no known cases in cattle.

"These findings suggest there could be U.S. states with A(H5)-positive people and animals that have not yet been identified," the study authors wrote, adding that the risk to the general public remains low.

While the infected veterinarians reported wearing gloves or clothing covers when caring for cattle, none wore respiratory or eye protection, which are recommended when working with uninfected animals in regions with confirmed cases. "HPAI A(H5) virus is known to be present in high concentrations in milk produced by infected cattle, introducing infection risk through respiratory, ocular, and gastrointestinal exposure," the researchers wrote. 

The current outbreak of H5N1 in dairy cattle was first detected in March 2024, with human cases identified infected dairy farm workers beginning in April. 

More herd and bulk-milk testing needed

The results also confirm the importance of preventing H5N1 infections in animals and rapidly identifying infected dairy cattle through herd and bulk milk-testing programs, as the US Department of Agriculture announced in October, the researchers said. 

Increased testing of herds and bulk milking tanks can help monitor for additional A(H5) positive herds and help better protect bovine veterinary practitioners and other animal workers.

"Increased testing of herds and bulk milking tanks can help monitor for additional A(H5) positive herds and help better protect bovine veterinary practitioners and other animal workers," they wrote. "Surveillance programs, such as herd and bulk milk testing and serosurveys, can aid in identifying areas of increased risk to bovine veterinary practitioners and workers to allow for appropriate engineering controls, administrative controls, and personal protection equipment use."