There are more than 20 viral species within the genus Hantavirus – the only pathogens of the family Bunyaviridae (enveloped, negative-sense single-stranded RNA) in vertebrates not associated with arthropod vectors. Instead, they are maintained in persistently infected rodents. Each virus is associated with a specific reservoir host (see Hosts for further information).
Hantaviruses are divided into two broad categories: Old World and New World viruses. In humans, Old World hantaviruses generally cause what is referred to as “haemorrhagic fever with renal syndrome” (HFRS) and New World hantaviruses cause “hantavirus pulmonary syndrome” (HPS). It should be noted, however, that both are multisystemic diseases and there can be significant overlap between these syndromes.