Disease ecology refers to the intricate human and environmental relationships that form the context of one or a group of diseases. Diseases are not simply biomedical entities; rather, they have their physical, environmental, sociocultural, psychological, and even political parameters. Distinctive human and biophysical environmental webs form the context of distinctive groups of human diseases. Major changes in this web, whether brought about by human intervention, environmental catastrophes, or a combination thereof, can result in a new context and possibly a new group of diseases. In developing countries, human control of the environment is limited, basic needs of a healthful life are not met, and, therefore, infectious and communicable diseases are the major cause of death. Improvements in health conditions will no doubt reduce the incidence of mortality resulting from infectious diseases and, in turn, bring about the prominence of chronic diseases more closely related to life-styles and life stages than to environmental parameters. South Asia as a geographic region still remains a region of poverty within which there is a marked contrast between the rural and urban genre de vie. Morbidity and mortality patterns in the rural and urban areas are, therefore, likely to be somewhat different, although paucity and quality of data make generalizations hazardous.

Ecologically, South Asia is one of the most distinctive regions of the world. Physiographically well demarcated, and climatically distinguished by the monsoonal rainfall regime, South Asian life has a rhythm marked by seasonality. Although agriculture is still the dominant occupation, rapidly swelling cities create air pollution, overcrowding, social stress, and the immense problem of waste disposal.