DES MOINES, Iowa — More than 4 million chickens in Iowa will have to be killed after a case of the highly pathogenic bird flu was detected at a large egg farm, the state announced Tuesday.

Crews are in the process of killing 4.2 million chickens after the disease was found at a farm in Sioux County, Iowa, making it the latest in a yearslong outbreak that now is affecting dairy cattle as well. Last week, the virus was confirmed at an egg farm west of Minneapolis, Minnesota, leading to the…