Epidemic Recurrence of Asian Influenza in Louisiana, 1959-1960

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Abstract
Epidemiologic observations were made of recurrent epidemic influenza A2 in rural areas and in selected urban groups in Louisiana in the winter of 1959-1960. Attack rates found were 32.0% in the school-family groups in Tangipahoa Parish, and 18.2% in the university and medical personnel in the city of New Orleans. These were considerably less than the 1957 incidence of Asian influenza but the rates of illness were the same whether or not there was a past history or record of the disease. Vaccine did not appear to reduce the incidence either, unless it was administered during the year of the epidemic. Certain differences betweenthe 2 epidemics were conspicuous. These included an inverse relationship in incidence of influenza in certain school, racial and age groups. Family size did not affect the numbers who became sick in the second epidemic. There were 15 isolations of influenza A2 and all strains were antigenically alike as determined by hemagglutination-inhibition and did not differ from a virus isolated in New Orleans in 1957. Hemagglutination-inhibition antibody was not detectable in most of the acute sera of those individuals in whom a serologic diagnosis of influenza was made.