One of the biggest threats today is the uncertainty surrounding the emergence of a novel pathogen or the re-emergence of a known infectious disease that might result in disease outbreaks with great losses of human life and immense global economic consequences. Over the past six decades, most of the emerging infectious disease events in humans have been caused by zoonotic pathogens--those infectious agents that are transmitted from animals to humans. In June 2008, the Institute of Medicine's and National Research Council's Committee on Achieving Sustainable Global Capacity for Surveillance and Response to Emerging Diseases of Zoonotic Origin convened a workshop. This workshop addressed the reasons for the transmission of zoonotic disease and explored the current global capacity for zoonotic disease surveillance.