The phenomenon of globally emerging infectious diseases requires understanding biological systems in the broadest sense and dealing with their extraordinary complexity. This includes processes operating at the level of transmission and evolution of a pathogen within and among host species and humans. It extends to and includes processes involving ecosystems and regional environmental change occurring on a global scale (2) . In fact the scale and magnitude of anthropogenic activity has reached a point of virtual co-dominance with natural processes of energy and material flows globally (3) .