Epidemiological Transition

The term “epidemiologic(al) transition” was coined by Abdel Omran in 1971 to refer to the shift from an infectious disease–dominated cause of death pattern to one in which chronic degenerative ailments predominate. As such, the epidemiological transition is one strand of a broader process of “demographic transition” comprising declining birth and death rates, population aging, changing morbidity patterns, increasing spatial mobility, rising urbanization, evolving labor force structure, and the like. Here, the basic propositions, successive stages, models of transition, and claimed determinants of disease promulgated by Omran are outlined first. Critiques and extensions of the theory are then addressed. The impression of smooth, uninterrupted progression through the transition conveyed by Omran is evidently false, and the continuation of epidemiological evolution beyond what was initially envisaged is explained. There is a tendency to underestimate the continuing burden of infectious disease mortality in present-day developed nations. The debate over the historic importance of different disease determinants is also discussed. This entry then explains the widening out of the original transition theory into a more encompassing “health transition” perspective combining both the mortality and morbidity sides of human health. It explains the “compression” versus “expansion” of morbidity debate about the quality of health over the years of additional life expectancy. The importance of recognizing subnational variations in epidemiological profiles is argued, and the particular difficulties posed by “epidemiological polarization” in many less developed countries are noted. Finally, the entry considers the utility of epidemiological transition theory for health planning and strategies.