Our review of ecological theory and the resulting complex model described here demonstrates the limitation of classical disease ecology and natural history. For example, without incorporation of population genetic theory in ecology as 'evolutionary ecology', along with the concepts of pathogen spillover and cross-scale ecosystem dynamics, classical disease ecology cannot explain recent emergence events like those involving HIV/AIDS, SARS, avian influenza, E. coli 0:157, dengue, malaria, West Nile virus, and Nipah virus, among others. The resurgence of vector populations, having acquired pesticide resistance and lost predators and competitors as natural controls after a regimen of inappropriate pesticide use, similarly is explained by modern ecology and evolutionary biology. This has direct application to control and intervention policies and practices. For example, it points to the need to adopt control strategies that integrate landscape and habitat management with careful rotation of targeted chemical and biological agents (30) . Developing such strategies requires detailed field studies, built on traditional natural history and classical disease ecology, but supplemented with advanced molecular techniques, as well as ecological research that takes into account the community and systems level dimensions of a particular pathogen-host complex.