Two commercial turkey farms in Iowa have been hit by the reemerging highly pathogenic bird flu, causing about 100,000 birds to be killed to prevent the disease from spreading.

The Iowa Department of Agriculture reported the infected commercial poultry flocks within weeks of a turkey farm in South Dakota and one in Utah reporting the first outbreaks in the U.S. since April, raising concerns that more would follow.

The U.S. Department of Agriculture shows 12 commercial flocks in South Dakota, Utah and Minnesota have been affected in October, totaling more than 500,000 birds.