Although essential to designing effective prevention and control programs, empirical field based, disease ecology has been neglected in recent years (18) . Fortunately, theoretical disease ecology, stimulated largely by the work of Anderson, May and others has flourished and led to a significant syntheses involving application of ecological-evolutionary biology to the study of infectious diseases (19, 20) . Parallel to this, systems ecology has begun to extend its domain by applying complexity theory to emerging infections with at least initial suggestions of its implications (6) . This development in particular, along with observations from several decades of applications of systems ecology to natural resources and economic development (8, (21) (22) (23) , have resulted in important insights of significant potential in understanding zoonotic disease emergence as a cross-scale process. This area uses complex systems theory applied to coupled, human-natural systems to explain how processes such as local phenomena can result in a cascade of effects ultimately reaching global proportions. The finding suggests this crossscale behavior is controlled by relatively few variables, and is mitigated by social and ecological resilience. The loss of this resilience in ecological systems is observed to lead inevitably to unpredictable events or the 'surprise' characteristic of complex systems generally. This combination of socialecological systems and resilience theory helps explain the unpredictability of disease emergence events. It represents another potentially useful area of application to understanding emerging infectious diseases along with those areas generally considered within the domain of ecology mentioned above: population ecology and genetics, community ecology, and systems ecology.