New CDC Report Says Bird Flu Spread Undetected in Veterinarians

A Feb. 13 report from the Centers for Disease Control and Prevention (CDC) revealed that three bovine veterinary practitioners unknowingly contracted highly pathogenic avian influenza (HPAI), also known as H5N1 or bird flu, last year.

In its Morbidity and Mortality Weekly Report, the CDC said that public health officials conducted a serosurvey among 150 bovine veterinary practitioners in September 2024. Three practitioners had evidence of recent infection with HPAI virus, including two without exposures to animals with known or suspected HPAI virus infections and one who did not practice in a U.S. state with known HPAI virus–infected cattle.

The current outbreak of HPAI among dairy cattle was first detected in March 2024, with human cases of HPAI among dairy farm workers identified beginning in April. Farm workers and bovine veterinary practitioners working with HPAI virus–infected cattle are at increased risk for HPAI exposure, said CDC; in the current outbreak, most human infections with HPAI have been mild and were detected through enhanced surveillance of persons working with affected animals, the agency added. One case has resulted in death.

SURVEY FINDINGS. The veterinarians surveyed by the CDC were recruited in-person at a veterinary conference and through emails to conference attendees. Participation was anonymous, and participants received a $50 gift card as compensation after the blood draw. The serosurvey was reviewed and approved by the Ohio Department of Health institutional review board.

Surveyed practitioners were tested for antibodies to recent HPAI virus infection. Participants reported their primary practice in 46 U.S. states (143) and Canada (7). Among survey participants, 82 (55%) practiced in states with HPAI virus–positive dairy herds, and 25 (17%) worked with dairy cattle with known or suspected HPAI infection.

Three survey participants had antibodies to HPAI suggestive of recent infection, according to the report; all were U.S.-based practitioners. None of the practitioners with positive results reported respiratory or influenza-like symptoms — including pink eye, a common symptom of bird flu — nor had any received testing for influenza since January 2024.

All three practitioners with positive 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 worked with dairy cattle with known or suspected HPAI infection; however, one practitioner did work with HPAI–positive poultry, said the report.

Two of the participants with a positive test result reported practicing in multiple U.S. states, and two practiced in states with known HPAI infection among cattle. However, one reported providing veterinary care to dairy cattle only in Georgia and to nondairy cattle in South Carolina, two states that have not reported bird flu infection in dairy cattle.

All three reported wearing gloves or a clothing cover when providing veterinary care to cattle, but not respiratory or eye protection.

Read the full report here.