Fil: Enria, Delia. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Briggiler, Ana M. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Pini, Noemí. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Levis, Silvana. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.In May 1993 a new clinical entity named hantavirus pulmonary syndrome (RPS) was first described in the United States during the investigation of an outbreak of a febrile disease of high mortality, characterized by acute respiratory insufficiency. RPS was found to be caused by a novel agent of the Hantavirus genus. Since the discovery of the disease, isolated cases and outbreaks of HPS have been registered all over the Americas, and other SNV-related hantaviruses (New World hantaviruses) were identified either causing human illnesses or circulating among native sigmodontine rodent species. In this chapter, we will discuss the clinical manifestations of New World hantaviruses, with an attempt to analyze the differences that have been observed among different geographic areas and viral genotypes.