Rift Valley fever virus (RVFV) is an arthropod-borne pathogen that often results in severe morbidity and mortality in both humans and livestock. As its geographic range continues to spread, it presents a real threat to naïve populations around the world by accidental introduction (e.g., the result of increased world travel) or a bioterror event. The lack of prophylactic and therapeutic measures, the potential for human-to-human transmission, and the significant threat to livestock associated with RVFV make infection with these pathogens a serious public health concern. Rift Valley fever epizootics and epidemics might rapidly overwhelm the capacities of the public health and veterinary medical communities to provide rapid diagnostic testing, distribution of countermeasures and adequate medical care.