The evolution of virulence and emerging diseases.

Insights into the evolution of virulence may aid efforts to control or even prevent emerging diseases. Specifically, dangerous pathogens can be distinguished from those that pose relatively little threat by identifying characteristics that favor intense exploitation of hosts by pathogens, hence causing high virulence. Studies to date have implicated several such characteristics, including transmission by vectors, attendants, water, and durable propagules. These insights may improve the return on investments in disease control by directing effort and resources to the most-dangerous emerging pathogens. The approach also should help us to identify those control measures that will guard against the future emergence of dangerous pathogens, even those that have not yet been identified.