CDC Reports First U.S. Human Case of H5N1 Bird Flu Linked to Dairy Cattle Exposure in Midwest Farm Worker

A Texas dairy farm worker was diagnosed with the first U.S. human case of H5N1 avian influenza linked to exposure to infected dairy cattle, officials said March 25. The Centers for Disease Control and Prevention confirmed the infection after the patient had direct contact with cattle presumed to carry the virus, marking the second human H5N1 case in the United States and the first associated with cattle rather than poultry or wild birds.

The Texas Department of State Health Services announced on March 25 that the infected dairy farm worker had direct contact with cattle presumed to be infected with avian influenza A(H5N1) prior to the onset of symptoms.

The Centers for Disease Control and Prevention confirmed the diagnosis through laboratory testing, marking the second human case of H5N1 ever identified in the United States and the first linked to exposure to dairy cattle rather than poultry or wild birds, according to CDC officials.

The patient’s primary symptom was eye inflammation, or conjunctivitis, with no severe respiratory illness reported at the time of the announcement, Texas DSHS said. The individual was described as “doing well” and receiving antiviral treatment consistent with standard influenza therapy. Health authorities reported the patient had been instructed to isolate to prevent potential onward transmission, although there was no evidence of efficient human-to-human spread of the virus, CDC spokespersons confirmed.

The infected worker was employed on a Texas dairy farm and had close, direct contact with sick dairy cows, which were later confirmed or presumed to be infected with H5N1, officials said. Prior to the human case, H5N1 had been detected in multiple dairy herds across several states, including Texas, Kansas, Michigan, and New Mexico, indicating a multistate outbreak in dairy cattle, according to CDC and state agriculture departments. CDC and Texas DSHS noted that the most plausible route of infection was exposure to secretions or excretions from infected cattle, particularly around the udder and milk, consistent with findings that H5N1 in cows was strongly associated with udder infection and milk contamination.

CDC classified the overall public health risk from H5N1 bird flu in the United States as “low” but emphasized that the risk was elevated for individuals with close, unprotected contact with infected animals, such as farm workers and veterinarians. There was no known person-to-person transmission of H5N1 in the U.S., including in connection with this Texas case, CDC officials said. Following the case, CDC continued active monitoring and testing of people with relevant animal exposures through national influenza surveillance systems to detect any unusual human flu activity.

The Texas case occurred amid a broader outbreak of H5N1 in U.S. dairy cattle, with confirmed affected herds in Texas, Kansas, Michigan, Idaho, South Dakota, New Mexico, Ohio, and North Carolina, according to CDC data. National records show that since early 2024, 71 human A(H5) infections have been reported in the United States, with 41 cases linked to exposure to dairy cattle. The total included two deaths. Experimental and epidemiological studies cited by CDC and academic sources found that H5N1 viruses in dairy cattle retained a strong preference for infecting birds and did not efficiently transmit via airborne routes between mammals, suggesting low pandemic potential in their current form.

Federal and state agencies, including CDC, the Food and Drug Administration, and Texas DSHS, have consistently stated that commercial milk remains safe for consumption. Pasteurization inactivates H5N1 virus, and milk from sick cows is required to be discarded or diverted, FDA officials said. Although viral fragments were detected in some commercial milk samples, FDA investigations confirmed these were non-infectious remnants and did not pose a direct consumer health risk. Public health guidance advises against consuming raw or unpasteurized milk and dairy products from infected or unknown-status herds due to theoretical exposure risks prior to pasteurization.

CDC recommends that workers on affected farms use appropriate personal protective equipment, including eye protection, masks or respirators, gloves, and protective clothing, and adhere to hygiene and biosecurity protocols when handling sick animals or contaminated materials. Authorities stress the importance of rapid reporting of illness in farm workers, prompt testing for influenza in symptomatic exposed individuals, and early antiviral treatment when H5N1 infection is suspected, as demonstrated in the management of the Texas dairy worker case.

The Texas DSHS alert and CDC confirmation have been incorporated into national situation summaries, distinguishing this case as the index human H5N1 infection linked to dairy cattle. Ongoing surveillance and research by CDC and academic partners continue to monitor the evolving outbreak and assess zoonotic transmission risks, with an emphasis on protecting agricultural workers and preventing further spillover events.