Michigan dairy worker becomes 2nd US case of bird flu linked to cattle outbreak

A dairy worker in Michigan has tested positive for H5N1, the highly pathogenic bird flu strain now circulating among cattle across the country. It is the second confirmed human infection linked to the outbreak in less than two months, following a similar case in Texas in early April. The worker, whose identity has not been disclosed, developed a mild eye infection—the same type of symptom that appeared in the Texas case. Both workers had direct contact with infected cattle before they fell ill.

The path to diagnosis was indirect. When the Michigan worker first submitted a nasal swab to state health officials, the test came back negative. But a subsequent eye swab, analyzed at a CDC laboratory in Atlanta, tested positive for the virus. The worker has since recovered. The Texas dairy worker, who became ill shortly after the virus was discovered in US cattle herds, also experienced eye inflammation and has fully recovered as well.

Dr. Natasha Bagdasarian, Michigan's Chief Medical Executive, emphasized that the state had responded swiftly to the case and that officials were monitoring the situation closely. She noted that there have been no signs of the virus spreading from person to person—a critical threshold that public health officials have been watching for since the outbreak began. The CDC reiterated on Wednesday that the discovery of this second case does not change its assessment that the risk to the general public remains low.

Still, the case is likely to intensify pressure on federal health agencies and the dairy industry to expand testing efforts. Both cattle and the workers who handle them need closer surveillance, according to reporting on the matter. The virus had been circulating among dairy cattle for approximately four months before it was detected, raising questions about how many animals and people may have been exposed without knowing it.

The Michigan infection marks the third human bird flu case ever documented in the United States. A poultry worker in Colorado tested positive in 2022. Globally, the picture is more alarming. An Australian child who had recently traveled to India was confirmed this week to have contracted bird flu—the first such case in Australia. The child fell ill in March and experienced a severe infection, though the child has since recovered. In other parts of the world, bird flu infections have sometimes progressed to pneumonia and death.

The CDC has announced plans to monitor H5N1 in both dairy cattle and poultry operations, as well as among workers with direct animal contact, through the summer months. The two US cases so far have been mild and both patients recovered, but the pattern of infection—eye rather than respiratory symptoms, detection through eye swabs rather than nasal ones—suggests the virus may be behaving differently in cattle-to-human transmission than it has in other contexts. That difference itself warrants close attention as officials try to understand what they are dealing with.