Hantaviruses are emerging viruses that cause persistent chronic infections in their small mammal hosts. When these viruses are transmitted to humans, they can cause two clinical syndromes, hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). The understanding of the epidemiology, pathogenesis and natural history of these viruses has improved in recent years. The number of reported hantavirus infections is increasing worldwide and new hantaviruses are being discovered in many countries, so they now represent a public health problem of global concern. It is believed that hantavirus infections might be underestimated due to the frequently asymptomatic and nonspecific mild infections they cause as well as the lack of simple standardized diagnostic laboratory methods. In this review the current concepts regarding the epidemiology, ecology, clinical presentation, pathogenesis, diagnosis, and treatment of the infections associated with these emerging human pathogens are presented.