Studies of the Community and Family: Acute Respiratory Illness and Infection

Respiratory infections are the most common cause of acute morbidity, and have been the subject of numerous studies performed both before and after the identification of the major etiologic agents. A variety of different approaches have been used depending on the type of illness being studied and the questions being asked. Some approaches have been hospital-based if the intent was to study the small proportion of infections that result in severe disease, as opposed to the full range of illnesses and infections that occur in the family and the community. Other approaches, while examining illnesses of all severities, have focused on children or other specific segments of the population. Most studies have had a longitudinal design, so that seasonal variation in incidence could be determined. This review will discuss investigations that examined the full range of respiratory illnesses. Morbidity alone was the focus of early studies, most of which were carried out during the era when knowledge of etiologic agents was limited. During that period, illness frequency and characteristics began to be established. Later investigations stressed etiology. Only a small number of studies have comprehensively examined illness incidence and agent-specific infection frequency in all household members. Such studies have also proved to be