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October 1960

Studies of the Epidemiology of Influenza as Demonstrated by Serum Pools: II. Evidence of Inapparent Influenza Infections and General Level of Population Resistance as Shown by the Antihemagglutinin Reaction in Serum Pools Collected by Random Sampling.

Arch Intern Med. 1960;106(4):496-512. doi:10.1001/archinte.1960.03820040034005

In a previous publication 1 we reported the results of a study of individual cases of influenza infection in the St. Louis area extending from 1943 to the period just prior to the onset of the Asian Influenza epidemic in 1957. Information was presented concerning the prevalence of the disease during each year and the antigenic characteristics of the strains of virus responsible for the outbreaks that were observed.

In many virus infections, such as poliomyelitis, it is known that for each case with clinical manifestations of disease there are many inapparent infections. The occurrence of inapparent infections in the case of influenza is obvious if it can be shown that an increase in antibodies against the prevalent strain of influenza virus occurs in the general population simultaneously with the recognition of clinical cases. It was felt that a study of antibody levels in large pools of unselected sera might