A genus of Bunyaviridae responsible for pneumonia and hemorrhagic fevers. At least seven members of the genus are thus far recognized: Hantaan, Puumala, Seoul, Prospect Hill, Thailand, Thottapalayam, and Sin Nombre viruses. Other species have not been classified as yet. Hantaan virus causes Korean hemorrhagic fever. Various rodent species are the asymptomatic carriers of these viruses, which are shed in saliva, urine, and feces. Human infection is direct, or by the respiratory route from contaminated specimens; person-to-person spread is thought to be rare. An outbreak of hantavirus infection, the hantavirus pulmonary syndrome (HPS), causing severe and often fatal pulmonary symptoms was identified in the Four-Corners region of the Southwestern United States in 1993 and the agent was subsequently named Sin Nombre virus.