Factors Influencing the Emergence of New (and “Old”) Diseases

Since its introduction in 1992, the paradigm that views the emergence of new human infections as a product of man-made ‘factors of emergence’ has been widely adopted. However, only some of these factors have been studied in depth. This article reviews three factors that have been characterized scientifically: changes in land use, travel and trade, and microbial adaptation and change. The introduction of new factors by the Institute of Medicine has created overlapping of domains for research. To adequately define the operation of man-made factors will require careful multidisciplinary research, and the development and testing of metrics to describe factors that operate alone and with other factors in the emergence of new infections.