Contagion Since H5N1, more commonly known as avian or bird flu, first appeared in commercial poultry and backyard flocks in the US in February 2022, the threat of the Highly Pathogenic Avian Influenza (HPAI) virus has wreaked havoc among the poultry and livestock industry for producers, veterinarians and government agencies.1
As of May 2025, the Centers for Disease Control and Prevention (CDC) reports that more than 169 million birds have been affected, and avian flu has been detected in flocks in all 50 states and Puerto Rico.2 The total number of egg-laying chickens during December 2024 averaged 373 million,3 according to the U.S. Department of Agriculture (USDA); however, in March 2025, the total layers in the U.S. was about 351 million.4 Since November 2024, the costs associated with the ongoing outbreak have exceeded $1.4 billion,5 including $1.25 billion in indemnity and compensation payments to producers whose flocks were culled.