The spread of highly pathogenic avian influenza (H5N1) continues in Michigan, most notably jumping to a human May 22, making it the second human case in the U.S.

The affected individual was a worker on a dairy farm where the virus has been identified in cows. The worker reported symptoms, nose and eye specimens were taken, and testing revealed the eye specimen to be positive for the virus.

The Centers for Disease Control says genetic analysis will look for any changes to the virus that could alter the agency’s risk assessment. Conjunctivitis (eye infection) has been associated with previous human HPAI infections, including in the first U.S. human case reported April 1 in Texas. The worker is being treated with a flu antiviral drug, the CDC reports.

Given the high levels of H5N1 virus in raw milk from infected cows, and the extent of the spread of this virus in dairy cows, additional human cases could be identified, the CDC reports. Sporadic human infections with no ongoing spread will not change the CDC risk assessment for the U.S. general public, which the CDC considers to be low.

On the dairy front, Michigan is up to nine counties and 19 cases of highly pathogenic avian influenza (HPAI), according to the Michigan Department of Agriculture and Rural Development.

Related:Michigan is hot spot for avian flu

The disease, generally carried by wild birds such as ducks and geese, causes cows to have de­creased lactation, low appetite and other symptoms, but it does not require them to be euthanized. Cows are removed from the milking herd, treated, and milk is appropriately discarded. Pasteurizing milk, which kills bacteria and viruses, ensures the safety of milk.

The infected cattle herds are located in central and west Michigan in nine counties: Ottawa, Allegan, Barry, Ionia, Clinton, Ingham, Montcalm, Gratiot and Isabella counties.

As of May 22, nine states have confirmed cases of HPAI in domestic livestock, according to USDA.

While no cows have died from the virus, the disease is lethal to birds, and Michigan has had an influx of cases in poultry in recent months. Avian flu is highly contagious.

Michigan, a net exporter of eggs and the seventh-largest egg-producing state in the country, has had 6,841,990 birds affected by avian flu, including 10 commercial operations and 27 backyard flocks.

Earlier, Herbruck’s Poultry Ranch, the largest poultry farm in the state, announced it would lay off 400 of its 1,200 employees after three operations were infected, resulting in more than 6 million birds having to be euthanized.