ACUTE UPPER RESPIRATORY INFECTIONS IN FAMILIES

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Abstract
A study was made of acute upper respiratory infections reported by 45 families during two periods each of 6-months duration. The main observations may be summarized as follows: Introduction rates were higher among children than among adult family members. Secondary attack rates varied according to the age of the index case, the latter being more influential. Some relation between secondary attack rates and degree of crowding in the household was found when the index cold occurred in a child under the age of 15 years. Tobacco smokers did not have higher secondary attack rates than non-smokers. The incubation period of noncoryzal illness with sore throat was longer than that of all other upper respiratory infections. When allowance was made for this fact, secondary attack rates did not vary according to the symptom type of the index cold. There were significant differences between adults and children under age 15 years in the distribution of symptom types. Among children under 15, but not among adults, the symptom type of secondary colds corresponded significantly to that of the index cold. Short-term immunity after attack was seen among preschool children and adults. Short-term increased susceptibility after attack was found among infants. No evidence was obtained that immunity can be acquired from subclinical infection. There appeared to be some correlation between the number of colds suffered by the same person in 2 successive years over and above individual differences in age and family size.