The isolation of avian influenza virus from chickens is reported for the first time in the United States since the fowl plague outbreak of 1929. The type-A virus was isolated from commercial Leghorn laying hens between 54 and 55 weeks old and involved three different farms in north-central Alabama. These flocks experienced up to 69% mortality and a severe decrease in egg production within a 14-day period.

The epidemiology of the first reported non-fowl-plague avian influenza (AI) virus, A/Chicken/Alabama/75 (Hav4Neq2), isolated from chickens in the United States is discussed. The signs and pathologic changes have been described. The environment, nutrition, and stress factors are discussed as possible contributors to the disease syndrome observed in 3 commercial egg-laying flocks. Avian influenza antibody was demonstrated by agargel precipitation in convalescent chickens through 83 days postinfection. A serological survey of 321 additional poultry flocks was negative for antibodies against avian influenza. A survey was made by serology and virus isolation techniques on 387 wild free-flying birds that fed and roosted in the area. Wild waterfowl are discussed as a possible source of the AI virus.

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