Several authors have categorized causal factors of infectious disease emergence, including explicitly citing 'ecological' ones involving land use change (9) (10) (11) (12) or 'land use drivers' (13) , human movement (10, 12) , encroachment and wildlife translocation (10, 11) , rapid transport (9, 10) and climate change (11, 12) . Most recently, the Institute of Medicine (1) described these along with others (13 categories of factors in all) and a model stating the major categories of factors have historically converged to bring about the current global emerging infectious disease crisis. Ecological factors are described as one of four major categories of factors that have converged with social, political, and economic factors; genetic and biological factors; and physical environmental factors. We take a different approach to understanding the interaction of the above factors and their causal relationships by focusing on disease emergence as an ecological-evolutionary phenomenon influenced by human factors. Our interest is in how human factors interact with natural processes and, in particular, how mechanisms operating at levels meaningful to understanding pathogen transmission and evolution can result in regional and ultimately global phenomena (i.e., regional endemism, epidemics, or global pandemics).