Hopkins-based Michael Foods has lost 12% of its egg supply after millions of egg-laying chickens were exposed to bird flu and euthanized at a contracted facility in Iowa, according to parent company Post Holdings.

Michael Foods is one of the nation's largest egg processors for restaurants and other foodservice outlets and as an ingredient for other food manufacturers. Post, which also owns Lakeville-based cereal and pet food maker Post Consumer Brands, said Monday the loss of nearly 4.5 million birds won't affect its financial outlook for the year ahead.

The Iowa Department of Agriculture & Land Stewardship said the outbreak in Sioux County was the state's first since July.

The virus is also still spreading in Minnesota, with about 300,000 turkeys euthanized on three Meeker County farms at the end of November after several months without a reported infection.

Since the highly pathogenic avian influenza outbreak began in February 2022, nearly 120 million birds have died or were culled to stop the spread of the virus nationwide.

Egg prices shot up to a national average of nearly $5 a dozen in January 2023 before sharply falling again. They've again been rising amid the lingering bird flu cases and high demand during holiday baking season. As of October federal data shows a carton now runs $3.37.

On Friday, the U.S. Department of Agriculture said it would begin testing milk for H5N1 virus particles in several states. Minnesota, Wisconsin and Iowa are not part of the first round of states having their milk supplies tested.

Human cases have been recorded among dairy and poultry workers who reported close contact with animals, but human-to-human transmission has not yet occurred.

However, a recent study in the journal Science concluded the current H5N1 strain could mutate to a human-to-human transmission threat.

"The findings demonstrate how easily this virus could evolve to recognize human-type receptors," said author Ting-Hui Lin, a postdoctoral associate at Scripps Research, in a news release. "However, our study doesn't suggest that such evolution has occurred or that the current H5N1 virus with only this mutation would be transmissible between humans."