to Asia, Australia, Europe, and eventually to the Americas, as we explored the ends of the Earth and beyond the confines of this planet, the vast entourage of animals, plants, and microbes that have accompanied us on our journeys has only amplified the impact of our species on every ecosystem that we have encountered.

Among these “fellow travelers,” pathogens have flourished in new surroundings, while other microbes have colonized incoming migrant host species. Such introductions, abetted by additional genetic, biological, social, and political factors associated with infectious disease emergence (see Box WO-1), have given rise to epidemics throughout recorded history (IOM, 2003; Morens et al., 2008). The current era of “globalization” affords frequent and widespread opportunities for disease emergence, several of which are described in detail in later sections of this overview. This section summarizes two presentations that opened the workshop by exploring the history and ongoing political and public health significance of human migration and mobility.

In his overview of the history of human migrations, speaker Mark Miller, a professor of comparative politics at the University of Delaware, emphasized migration’s growing political importance (see Miller in Chapter 1). Considering