Michigan farmworker becomes 2nd US case of bird flu tied to dairy cow outbreak

A Michigan dairy worker has contracted bird flu through direct contact with infected cows, becoming the second person in the United States to catch the virus from livestock during an outbreak that has now spread across nine states.

The male farmworker developed what he described as a gritty sensation in his eye earlier in May. Health officials confirmed the infection through an eye swab taken on Tuesday, which tested positive for H5N1, while a nasal swab came back negative. This pattern of results pointed to a localized eye infection rather than a systemic illness. According to Dr. Natasha Bagdasarian, Michigan's chief medical executive, the case was mild. The worker did not require oseltamivir, the antiviral medication typically recommended for bird flu treatment, and has since recovered.

The discovery marks a significant moment in the unfolding dairy outbreak. Since late March, when bird flu was first detected in U.S. cattle, the virus has established itself in 51 dairy herds spread across nine states. Michigan alone accounts for 15 of those herds. The first human case tied to the dairy outbreak occurred in Texas in late March, when a farmworker there also developed eye inflammation and recovered. Before that, a Colorado prison inmate had contracted H5N1 in 2022 while working at a poultry farm, though that case predated the livestock outbreak.

Health officials have been methodical in their response. Since the first cow cases emerged, they have tested 40 people with potential exposure to infected animals. Michigan has conducted 35 of those tests. The state's approach has been notably proactive: officials there have been sending daily text messages to exposed farmworkers asking about symptoms, a practice that Dr. Nirav Shah of the CDC credited with helping catch this infection. No other workers have reported illness so far.

The risk to the general public remains low, health officials say, but farmworkers who handle infected animals face elevated danger. The virus has been found in high concentrations in the raw milk of infected cows, yet government agencies have confirmed that pasteurization—the heat treatment applied to milk sold in grocery stores—kills the virus, making commercial dairy products safe. The concern centers on occupational exposure, particularly through the eyes and respiratory tract. Officials have recommended that farmworkers be offered protective equipment, though it remains unclear whether the Michigan worker was wearing eye protection at the time of infection.

Michael Osterholm, an epidemiologist at the University of Minnesota who has spent decades studying bird flu, offered a cautiously optimistic assessment. There is no evidence that the virus is causing serious 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. Dr. Shah acknowledged that more infections among farmworkers are possible as the outbreak continues, but the pattern so far—two cases, both mild, both localized to the eye—suggests the virus has not adapted to spread efficiently among humans.

The broader context underscores why officials are watching closely. Since 2020, the bird flu virus has been jumping between species at an accelerating pace, infecting dogs, cats, skunks, bears, seals, and porpoises across dozens of countries. The detection in U.S. dairy cattle earlier this year was unexpected and raised immediate questions about food safety and pandemic potential. That the virus has so far remained contained to mild eye infections in the two farmworkers exposed to infected cows is, for now, the best available evidence that the outbreak has not crossed a dangerous threshold. But the investigation continues, and health officials are preparing for the possibility that more cases may emerge.