Hantaviruses (or orthohantaviruses) are a family of RNA viruses in the Bunyavirales order. The enveloped virion is 120–160 nm in diameter and contains a single-stranded, negative-sense RNA genome with three segments. They infect many species of rodents, as well as shrews and moles, without causing disease, and can be transmitted to humans, where they can cause serious disease. Hantaan virus, the first known hantavirus, was discovered in 1976 as the cause of a novel haemorrhagic fever affecting combatants in the Korean War; it can also be caused by other hantaviruses, including Dobrava-Belgrade and Seoul viruses. Some hantaviruses, including Sin Nombre and Bayou, cause a pulmonary syndrome. Others have not yet been associated with human disease.
Unlike other bunyaviruses, hantaviruses are not transmitted by arthropods. Rodents act as the vector, with transmission to humans usually occurring via contact with urine, saliva or faeces, by inhalation of aerosolised excreta or by bite. Little is understood about how hantaviruses cause disease; the main site of viral replication in the body is unknown. Rodent control is important in disease prevention.