DES MOINES, IOWA — The Iowa Department of Agriculture and Land Stewardship announced on May 28 the state’s first detection of highly pathogenic avian influenza (HPAI) in 2024.

The US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) confirmed a commercial layer flock in Sioux County, Iowa, tested positive for the disease. A total of 4.2 million hens were affected.

“The Iowa Department of Agriculture and Land Stewardship is strongly encouraging Iowa poultry producers and dairy farmers to bolster their biosecurity practices and protocols to protect their flocks and herds,” the agency said, adding that protection for workers in contact with poultry and dairy cows is also important to limit further transmission.

Iowa’s most recent HPAI case in a commercial flock before this one also occurred in Sioux County. The outbreak on Nov. 28, 2023, affected 1.6 million layer chickens.

Since the beginning of the HPAI wave, 23.1 million birds in Iowa have been affected.

This article has been updated to reflect the number of birds affected by the latest HPAI outbreak in Iowa.