Toward an Epidemiological Model of AIDS in Sub-Saharan Africa

The outbreak of AIDS around the world in the last 15 or 20 years is usually referred to as the “AIDS epidemic,” or occasionally “pandemic” (Grmek 1990). These terms have no great analytic value. The major medical dictionaries and epidemiological textbooks define an epidemic merely as an outbreak of a disease marked by a greater number of cases than usual (see Fox et al. 1970: 246–49; Mausner and Bahn 1974: 22, 272–77;Stedman’s Medical Dictionary1977: 470; Kelsey et al. 1986: 212; Walton et al. 1986: 351; Harvard 1987: 247). This condition is contrasted with the endemic form of a disease at “its habitual level, or what previous experience would lead one to anticipate.” The termpandemicis used to describe an epidemic widespread in the world and usually characterized by a large number of cases, for example, the fourteenth-century plague epidemic (or Black Death) and the influenza epidemic during the latter part of World War I. Some authorities stress the fact that epidemics are also characterized by a declining phase. This is true by definition, of course, for otherwise the disease could be described as shifting to a new and higher endemic level. But it is also of interest that most of these unusual outbreaks of disease are eventually limited by such mechanisms as a decrease in susceptibles as persons become immune or die; as interventions, either medical or behavioral, eliminate the source or interrupt transmission; or as the pathogen mutates and becomes less virulent.