FACTORS IN THE EMERGENCE OF INFECTIOUS-DISEASES

''Emerging'' infectious diseases can be defined as infections that hav e newly appeared in a population or have existed but are rapidly incre asing in incidence or geographic range. Among recent examples are HIV/ AIDS, hantavirus pulmonary syndrome, Lyme disease, and hemolytic uremi c syndrome (a foodborne infection caused by certain strains of Escheri chia coli). Specific factors precipitating disease emergence can be id entified in virtually all cases. These include ecological, environment al, or demographic factors that place people at increased contact with a previously unfamiliar microbe or its natural host or promote dissem ination These factors are increasing in prevalence; this increase, tog ether with the ongoing evolution of viral and microbial variants and s election for drug resistance, suggests that infections will continue t o emerge and probably increase and emphasizes the urgent need for effe ctive surveillance and control. Dr: David Satcher's article and this o verview inaugurate ''Perspectives,'' a regular section in this journal intended to present and develop unifying concepts and strategies for considering emerging infections and their underlying factors. The edit ors welcome, as contributions to the Perspectives section, overviews, syntheses, and case studies that shed light on, how and why infections emerge, and how they may be anticipated and prevented