360 INFLUENZA A AND B VIRUS INFECTION IN INFANTS AND YOUNG CHILDREN DURING THE YEARS 1957–1976

Abstract

Influenza A virus activity was demonstrated in infants and young children from metropolitan Washington, D. C. during each of 19 successive August-July respiratory disease years, and during 17 of these years at least two per cent of hospitalized respiratory disease patients yielded an influenza A or B virus and/or showed an influenza A or B serum complement fixing (CF) antibody response. Between October 1957 and July 1976, 14.3 per cent of 860 croup patients and 5.3 per cent of 5,655 hospitalized respiratory patients showed evidence of influenza A or B virus infection. Serious illness with influenza A virus was 4.5 times more common than with influenza B virus. Influenza A virus infections were seen more than twice as frequently during the era of the H3N2 virus subtype as during the H2N2 era. Patients with serious influenza A virus infections were especially likely to have croup (particularly during the H3N2 era), to be seen during December through February, and to be black male infants. During the peak month of a composite of 13 consecutive influenza A virus outbreaks, influenza A virus infection was demonstrated in 67.6 per cent of croup patients and 35.6 per cent of all hospitalized respiratory patients. During the peak month of a composite of 6 consecutive influenza B virus outbreaks, influenza B virus infection was demonstrated in 36.0 per cent of croup patients and in 10.8 per cent of all hospitalized respiratory disease patients