Tecumseh study of illness. XIII. Influenza infection and disease, 1976-1981.
The occurrence of influenza was followed in Tecumseh, Michigan during the five year period 1976-1981 by identifying onset of acute respiratory illness and by virus isolation and serology. Type B outbreaks were observed in 1976-1977 and 1979-1980, type A (H3N2) in 1977-1978 and 1980-1981, and type A (H1N1) viruses in 1977-1978, 1978-1979, and 1980-1981. Evidence of low level circulation of viruses in the year preceding an outbreak was not obtained. Age-specific isolation rates from specimens collected by the community physicians differed from age-specific isolation rates from specimens collected from the surveillance, suggesting the operation of a selection mechanism in the former. Symptoms associated with virus isolation were strongly influenced by age. Within age groups, several variables, especially median duration, indicated type A (H3N2) had produced the most severe illnesses, type A (H1N1) the mildest, with type B intermediate. Age-specific infection rates determined by serology for the 1976-1977 and 1977-1978 influenza seasons confirmed the consistently high rates for type A (H3N2) in children with some fall-off with increasing age. Type A (H1N1) rates peaked in children aged 5-19 years and type B in children aged 5-14 years. This may be related in part to insensitivity of the hemagglutination inhibition test in those under age 5 years. Infection with type A (H1N1) was detected at low frequency in adults. Pathogenicity was calculated based on the serologic data. It was estimated for all ages combined that, at a minimum, type A (H3N2) infection produced febrile illness in 25% of cases and type B infection produced respiratory illness in 34% of cases.
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000914:Antibodies, Viral / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000276:immunology / Q000302:isolation & purification; D009981:Influenza B virus / Q000276:immunology / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000209:etiology / Q000276:immunology; D008137:Longitudinal Studies; D008824:Michigan; D008875:Middle Aged; D012698:Serologic Tests / Q000379:methods
D000914:Antibodies, Viral