Despite the fact that migratory waterfowl are now established in their summer breeding grounds, outbreaks of highly pathogenic avian influenza (HPAI) persist.  The latest case in Maricopa County, AZ, involving a complex of 2.3 million hens indicates the persistence of infection.  Sequencing of the implicated virus will determine whether it is an avian-related D1.1 or a cattle B3.13 strain that will provide evidence of the source and route of infection.  The outbreak in Arizona was preceded by an April 30^th case involving 0.6 million hens in Aurora, SD. 

The severe losses that have occurred in 2025 to date include 33.2 million egg-producing hens on 60 farms or complexes. The incidence rate has obviously declined over the past three months but diagnosed outbreaks persist.  Growing turkeys are affected along with individual and obviously under-reported cases in backyard flocks.  Isolation of H5N1 avian influenza virus from live bird markets confirms the presence of undiagnosed supply flocks. Based on the absence of reports there is no certainty that USDA-APHIS is conducting traceback investigations to identify the source farms supplying live markets along the Atlantic seaboard.  The APHIS dashboard relating to detection of highly pathogenic avian influenza in wild birds updated on May 13, indicates isolation of H5N1 virus with a Eurasian genome from diverse states involving both waterfowl, black vultures  during Q1 and swallows during January.

Outbreaks among commercial and backyard flocks since February are indicated below:

This table confirms a declining incidence rate of cases among commercial flocks but unlike previous epornitics, outbreaks have persisted during late spring.

For 2025 to date, and based on an egg -producing population of 285 million hens, losses have attained:

Losses among caged hens are disproportionately high due to the effect of individual large complexes being affected.  Among the cage-free losses most were in large aviary complexes.  Organic and other cage-free hens in barns and in small commercial flocks were relatively unaffected despite regular feed delivery, egg collection and relatively lower levels of biosecurity as compared to in-line complexes.

Despite the USDA whack-a-mole approach to eradication and for the past three years as a program of control, highly pathogenic avian influenza has become endemic in the U.S. High risk areas include wetlands where migratory waterfowl congregate and along the four major flyways.  Although rapid flock depopulation has apparently reduced inter-flock transmission, it is obvious that virus is introduced into large complexes with power ventilation, whether caged or aviary housed, by the aerogenous route. Additional mechanisms include infected rodents, defects in biosecurity, transport and vaccination crews.

For the past three years, the industry has suffered from a lack of epidemiologic information relating to risk factors and specific routes of introduction of virus. It is known that APHIS in conjunction with federal and state wildlife agencies has conducted surveys on free-living mammals and birds in the vicinity of outbreaks on large complexes.  Results have yet to be published. These deficiencies have impeded the design and implementation of innovative methods of protection including vaccination.

Responding to high egg prices and escalating costs for control, the USDA announced a ‘five-pronged’ approach to address HPAI that effectively offered nothing new especially in the immediate and short-term. The program studiously avoided adoption of vaccination as an adjunct to biosecurity alone that clearly fails to offer absolute protection from infection.