Second U.S. farmworker diagnosed with bird flu linked to dairy cattle outbreak

A Michigan dairy worker has contracted bird flu from infected cattle—the second person in the United States to catch the virus through direct contact with sick cows. The man, who worked on a farm housing infected animals, developed what he described as a gritty sensation in one eye earlier this month. An eye swab tested positive for H5N1 on Tuesday, while a nasal swab came back negative, indicating the infection was localized to his eye. The symptoms were mild enough that he required no antiviral medication and has since recovered, according to Michigan's chief medical executive, Dr. Natasha Bagdasarian, and federal health officials who announced the case Wednesday.

This second case follows a similar infection in Texas in late March, when another farmworker developed eye inflammation after handling infected cattle. That patient also recovered without serious complications. Both cases represent an unexpected turn in the bird flu story: for the first time anywhere in the world, the virus has jumped from a mammal—specifically dairy cows—to humans. Until this year, H5N1 had spread among birds and, more recently, among various wild and domestic animals including dogs, cats, skunks, bears, seals, and porpoises across dozens of countries. The appearance in U.S. livestock raised immediate concerns about food safety and the potential for the virus to establish itself in human populations.

So far, that hasn't happened. The outbreak in dairy herds has grown steadily but remains confined to cattle. As of Wednesday, the virus had been confirmed in 51 dairy herds across nine states, with Michigan bearing the heaviest burden at 15 infected herds. Federal officials have tested 40 people with potential exposure since the first cow cases emerged in late March; Michigan alone has screened 35 of them. The state's aggressive approach—sending daily text messages to exposed farmworkers asking about symptoms—appears to have caught this second case early. No other workers have reported illness.

Health officials emphasize that the risk to the general public remains low. Pasteurized milk sold in stores is safe to drink; heat treatment has been proven to kill the virus, even though raw milk from infected cows contains high levels of it. The real concern centers on farmworkers themselves, who face direct exposure to infected animals and their bodily fluids. Officials are now recommending that such workers be provided protective equipment, particularly eyewear, though it remains unclear whether the Michigan worker was wearing any protection at the time of infection. An investigation into the circumstances is ongoing.

Dr. Nirav Shah of the CDC called the case "not unexpected" and acknowledged that more infections among farmworkers are possible as exposure continues. Yet epidemiologists studying the situation see reason for cautious optimism. Michael Osterholm, a University of Minnesota researcher who has tracked bird flu for decades, noted that there is no evidence the virus is causing respiratory illness or spreading from person to person. "If we had four or five people seriously ill with respiratory illness, we would be picking that up," he said. The absence of such cases, combined with active surveillance efforts in Michigan and elsewhere, suggests the virus has not yet adapted to human transmission.

This is the third documented case of H5N1 infection in the United States overall. In 2022, a Colorado prison inmate working at a poultry farm in Montrose County contracted the virus while processing infected birds; his only symptom was fatigue, and he recovered fully. That case predated the emergence of bird flu in dairy cattle. The pattern across all three American cases is consistent: localized symptoms, rapid recovery, no need for intensive treatment. Whether that pattern holds as more farmworkers potentially encounter infected herds remains the central question health officials are watching.