The title of this introductory chapter would have amazed the medical student I was in the 1970s. In that pre-AIDS era of medicine, infectiology was the emblem of triumphant medicine, with the icon names of Jenner, Pasteur, Koch, and Flemming, among others.The student who chose to specialize in this field appeared to be opting for the easy road to fame and fortune. This is no longer true and in the past has been so only for the industrial world.The peril of emerging and reemerging infectious diseases (ERID) was clearly identified by the US health and political authorities more than 10 years ago. This was before the mad cow disease, foot-and-mouth disease, SARS, and avian flu affairs.