Enlarge / Holstein cows at a dairy farm. (credit: Getty | John Carl D'Annibale)

Another dairy farm worker in Michigan has been infected with avian influenza virus, state and federal health officials reported Thursday.

The case marks the third time the outbreak of bird flu in milking cows is known to have spilled over to a human. The dairy farm worker in Michigan, like the others, had close contact with H5N1-infected dairy cows, suggesting another case of cow-to-human transmission.

But the case reported today is notable for being the first one involving respiratory symptoms. In the first two cases, the dairy workers (one in Texas, the other in Michigan) reported only eye infections (conjunctivitis). This third case—also in Michigan but from a different farm—reported upper respiratory symptoms, including cough, congestion, and sore throat, as well as eye discomfort and watery discharge, but not conjunctivitis. The worker was given an antiviral (Tamiflu) and is said to be recovering. No other workers on the farm have shown symptoms, and the worker's household contacts are being monitored.