This study analyzed the importance of zoonoses and communicable diseases common to man and animals as potential Public Health Emergencies of International Concern to build an evidence base for future efforts to reduce risk of infection at the animal/human health interface. The events recorded in the World Health Organization (WHO) Event Management System (EMS) database for the Americas during the 18 months since the implementation of the 2005 revised version of WHO's International Health Regulations (15 June 2007-31 December 2008) were the main source for this analysis. Of the 110 events recorded by the EMS for the Americas during the study period, 86 were classified as communicable diseases-77 (70.0%) "within the animal/human health interface," 9 (8.2%) "not common to man and animals," 16 (14.5%) "syndromes with unknown etiologies," and 8 (7.3%) "product-related/ other." Of the 77 events within the animal/human health interface, 48 were "substantiated" (the presence of hazard was confirmed and/or human cases occurred clearly in excess of normal expectancy). These results confirm previous research and underscore the importance of the animal/human health interface as well as inter-sectoral collaboration.