In this portion of the panel I shall discuss the epidemiological aspects which have a bearing on the therapy and prevention of upper respiratory tract diseases. Many efforts have been made to prevent upper respiratory tract diseases by immunization and by attempts to break the chain of transmission. The purpose of this paper is to show, on epidemiological grounds, why these attempts have failed and to indicate the points that must be understood before actual prevention can be achieved.
First, it is necessary to define what is meant by upper respiratory tract disease. I shall include under this term all the nonspecific infections that involve the upper respiratory tract and recognize the fact that in a large proportion of theseillnesses the lower respiratory tract is also involved. The scope of the problem is illustrated in the first table, which shows the experience of a group of normal families which my