Chicken confinement operators are trying to find the most humane and safe way to kill and dispose of 3.8 million egg-laying hens, the Des Moines Register reported. “It’s a huge undertaking,” John Clifford, the U.S. Department of Agriculture’s chief veterinary officer, said during a press update last week.

An Osceola County operation in northwest Iowa is the largest in the nation to test positive for avian influenza. Sonstegard Foods Co., based in Sioux Falls, S.D., confirmed last week that bird flu was discovered at Sunrise Farms, an egg-laying operation affiliated with the company. Sick birds typically are suffocated with carbon dioxide or a foam, then must be composted, rendered or buried to prevent the illness from spreading.