Epidemiology Of Arenaviruses In The Americas

To date, a total of 16 different indigenous arenaviruses have been identified in the Americas. Four of these agents (Junin, Machupo, Guanarito and Sabia) an associated with severe hemorrhagic disease in humans. Based on their antigenic and phylogenetic relationships, the New World arenaviruses segregate into three distinct genetic lineages within the Tacaribe complex. The four New World arenaviruses associated with hemorrhagic fever fall within genetic lineage B and all have rodents as their primary vertebrate hosts. The hemorrhagic diseases associated with these four viruses are clinically indistinguishable: sporadic and cyclical in occurrence, and quite focal in their geographical distributions. Studies of their rodent hosts indicate consistently high rates of natural infection within the endemic focus, but little or no infection among the same rodent species outside of the endemic zone. These and other aspects of the unique epidemiology and ecology of this interesting group of zoonotic viruses are discussed. New data are also presented from recent field studies on the ecology of Guanarito and Pirital viruses in Venezuela.