Bird flu that hit Minnesota farms this spring caused egg production to drop 14 percent in May compared with the previous month.

The average number of layer hens in the state was also down 14 percent in May compared with April, and down 7 percent from May 2014, according to the latest figures from the U.S. Department of Agriculture.

“It’s not unexpected given the number of facilities that have been hit in Minnesota,” said Steve Olson, executive director of trade groups for Minnesota’s egg farmers and turkey growers. “We would expect to see a drop in production both in hen numbers and in eggs produced.”

Minnesota has the nation’s eighth-largest egg-laying industry. Four Minnesota egg farms were wiped out by the flu between late April and mid-May, and about 3.6 million hens were euthanized.

Olson said no “hard dollar figure” has been attached to the losses.

“We expect that it will take a year and a half to two years for those operations to be back to full production again,” he said.

Contaminated farms need to go through the process of depopulation, cleaning and disinfection, and environmental testing before flocks can be restocked.

Olson said it takes longer to restock egg farms than turkey barns. Unlike turkeys raised for meat, chicken populations are staggered so that all hens are not the same age, he said.

In total the H5N2 virus has struck 108 farms in 23 counties in Minnesota, almost all of them confined turkey operations. More than 9 million birds have been killed.

While highly contagious and deadly to domestic poultry, animal health officials say the bird flu is not a food hazard and is a very low risk for human health.

The last report of any poultry flock becoming infected in the state was on June 5. Experts have said for months that the spread of the virus should drop off because it does not survive in warmer weather.

The latest report showed higher losses in Iowa, the nation’s top egg producer. The number of eggs produced there dropped 21 percent between April and May, to the lowest level since early 2005.

More than 31 million birds have been killed in Iowa, mostly on egg farms. However, the large losses in the Midwest have not meant disaster for the national egg market, where egg production was down about 5 percent in May compared with the same month in 2014.

“The national [egg] numbers are tempered because of other production elsewhere in the country,” Olson said.