Enlarge (credit: Getty | David Paul Morris)

A second Colorado poultry farm has reported a case of bird flu in a worker, marking the state's seventh human case this month amid the ongoing outbreak among dairy cows.

Colorado health officials said the seventh case is, for now, a presumptive positive. That means that the person has tested positive at the state level while confirmatory testing is being carried out at the Centers for Disease Control and Prevention.

The presumptive positive worker was at a poultry facility in the state's northeastern Weld County. In recent weeks, six workers at another poultry farm in Weld also tested positive for bird flu. In that facility, a commercial egg layer operation with about 1.8 million birds, workers were infected as they culled chickens known to be infected with the highly pathogenic avian influenza. Genetic testing of the virus in the birds and the workers indicated that they were infected with a strain of H5N1 closely related to the virus found spreading in dairy cattle and to dairy farm workers.

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.