HONG KONG INFLUENZA: THE EPIDEMIOLOGIC FEATURES OF A HIGH SCHOOL FAMILY STUDY ANALYZED AND COMPARED WITH A SIMILAR STUDY DURING THE 1957 ASIAN INFLUENZA EPIDEMIC1
Davis, L E., G. G. Caldwell, R. E. Lynch, R. E. Bailey and T. D. Y. Chin (Ecological Investigations Program, NCDC, 2002 W. 39 St., Kansas City, Kans. 66103). Hong Kong influenza: the epidemiologic features of a high school family study analyzed and compared with a similar study during the 1957 Asian influenza epidemic. Amer. J. Epid., 1970, 92; 240–247.—A retrospective questionnaire survey of 6, 994 students from a high school in Kansas City, Mo. and their families, for histories of influenza-like illness was conducted during the 1968–1969 epidemic of Hong Kong influenza. The overall clinical attack rate was 39%. The age-specific attack rates of all age groups were similar. The secondary age-specific attack rate curve also had a flat configuration, possibly indicating that all age ranges were equally susceptible to Hong Kong influenza. These results were compared with those of a similar survey at the same high school following the 1957 Asian influenza epidemic. In contrast, school children in the 1957 epidemic experienced significantly higher clinical attack rates than adults. In 1957, the epidemic spread primarily within schools; a school child was flve times as likely as an adult to have introduced the illness into the family. In the Hong Kong influenza epidemic, however, the virus appeared to have spread initially both in schools and in the community; an adult was as likely as a school child to have been the first family case. This dual mode of primary spread weakens the suggestion that vaccination of school children would abort an influenza epidemic