Fil: Young, J. C. US Department of Health and Human Services. Public Health Service. Centers for Disease Control and Prevention. National Center for Infectious Diseases. Division of Viral and Rtckettsial Diseases. Spectal Pathogens Branch, Atlanta, Georgia; Estados Unidos.Fil: Mills, James N. US Department of Health and Human Services. Public Health Service. Centers for Disease Control and Prevention. National Center for Infectious Diseases. Division of Viral and Rtckettsial Diseases. Spectal Pathogens Branch, Atlanta, Georgia; Estados Unidos.Fil: Enria, Delia A. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Dolan, N. E. US Department of Health and Human Services. Public Health Service. Centers for Disease Control and Prevention. National Center for Infectious Diseases. Division of Viral and Rtckettsial Diseases. Spectal Pathogens Branch, Atlanta, Georgia; Estados Unidos.Fil: Khan, Ali S. US Department of Health and Human Services. Public Health Service. Centers for Disease Control and Prevention. National Center for Infectious Diseases. Division of Viral and Rtckettsial Diseases. Spectal Pathogens Branch, Atlanta, Georgia; Estados Unidos.Fil: Ksiazek, Thomas G. US Department of Health and Human Services. Public Health Service. Centers for Disease Control and Prevention. National Center for Infectious Diseases. Division of Viral and Rtckettsial Diseases. Spectal Pathogens Branch, Atlanta, Georgia; Estados Unidos.Since the intial description in 1993 of hantavirus pulmonary syndrome and its novel aetiological agent, Sin Nombre virus, our knowledge of the epidemiology of New World hantaviruses has continued to evolve. After the identifying outbreak in the southwestern US, four hantaviruses have been identified in North America with specific rodent hosts and associated with a number of sporadic cases. This stability of case recognition in North America is in contrast to the multiple outbreaks and endemic cases in South America. Despite a plethora of New World hantaviruses and new evidence of person-to-person transmission, the ecological and personal determinants of this human infection remain a mystery.