Morbidity and Mortality Characteristics of Asian Strain Influenza

Abstract

A survey of 5822 high school students and their families during the fall epidemic revealed an attack rate of 34%. The highest attack rate was observed in persons aged 10-19 years, the rate declining with increasing age. The rate of clinical infection varied according to family size from 30.7% in 3-member households to 40.5% in households with 7 or more members. The secondary attack rate was 14%. A total of 253 deaths due to influenza and pneumonia was reported in Kansas City, Mo., from October 1, 1957 to March 31, 1958, a mortality rate of 49.6 per 100,000. This rate was 2 to 3 times higher than that of the 4 preceeding noninflu-enza years. Deaths from all causes also increased. Two peaks were observed in the mortality curve, one occurring in October and November and the secondary peak in the latter part of February. Highest death rates were observed in the very young and the very old. Of the persons who died 73% had a history of preexisting chronic disease or other associated conditions, the majority of which were listed as cardiovascular or chronic pulmonary disease.