Results of a serosurvey conducted by the Centers for Disease Control and Prevention (CDC) published Thursday indicate three U.S. bovine veterinary practitioners had recently been infected with highly pathogenic avian influenza (HPAI) A(H5).
The three individuals were part of a CDC serosurvey of 150 bovine veterinary practitioners. The survey was conducted between Sept. 12-13, 2024.
The veterinarians participating in the survey were tested for HPAI A(H5) antibodies that would indicate past infection and asked about their cattle exposure in the past three months. Additionally, their exposures since January 2024 were assessed.
One of the three practitioners with positive serology results practiced in only two states – Georgia and South Carolina. Neither of those states has had a known HPAI A(H5) virus infection in cattle and there have been no reported human cases.
“This practitioner reported no exposures to animals with known or suspected HPAI A(H5) virus infections,” the CDC said in its Morbidity And Mortality Report on Thursday.
“These findings suggest that there might be HPAI A(H5) virus–infected dairy cattle in states where infection in dairy cattle has not yet been identified, highlighting the importance of rapid identification of infected dairy cattle through herd and bulk milk testing as recently announced by the U.S. Department of Agriculture,” authors of the report said.
The CDC says all three practitioners with positive serology results provided care to multiple animals, including dairy cattle; two also provided care to nondairy cattle, one provided care to poultry, and one worked at livestock markets.
None of the three veterinarians worked with dairy cattle known or suspected to have anHPAI A(H5) virus infection. However, one practitioner did work with HPAI A(H5) virus–positive poultry. Two of the participants with a positive serologic test result reported practicing in multiple U.S. states, and two practiced in states with known HPAI A(H5) infection among cattle.
The practitioners all reported wearing gloves or a clothing cover while caring for cattle but did not report wearing respiratory or eye protection.
Since the time that this serosurvey was conducted, the HPAI A(H5) outbreak has expanded to include 67 confirmed human cases, including 40 with dairy cattle exposure, the CDC said.
However, there is no evidence that “bird flu” is spreading from person to person. The CDC says the risk to the public remains low, although people who work on farms and with infected animals, or who have backyard poultry flocks, are at higher risk of infection.
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Reference
Leonard J, Harker EJ, Szablewski CM, et al. Notes from the Field: Seroprevalence of Highly Pathogenic Avian Influenza A(H5) Virus Infections Among Bovine Veterinary Practitioners — United States, September 2024. MMWR Morb Mortal Wkly Rep 2025;74:50–52. DOI: http://dx.doi.org/10.15585/mmwr.mm7404a2
