Guarding against the most dangerous emerging pathogens.

Control of emerging infectious diseases will be difficult because of the large number of disease-causing organisms that are emerging or could emerge and the great diversity of geographic areas in which emergence can occur. The modern view of the evolution of pathogen virulence--specifically its focus on the tradeoff between costs and benefits to the pathogen from increased host exploitation--allows control programs to identify and focus on the most dangerous pathogens (those that can be established with high virulence in human populations).