Puumala virus (PUUV) is a species of hantavirus. Humans infected with the virus may develop a haemorrhagic fever with renal syndrome (HFRS) known as nephropathia epidemica. Puumala virus HFRS is lethal in less than 0.5% of the cases. Puumala virus is named after a municipality in Finland. The virus is found predominantly in Scandinavia and Finland, although it has also been reported elsewhere in Northern Europe, Poland and Russia. Because the bank vole (Myodes glareolus) acts as a reservoir for the virus, nephropathia epidemica cases track with the vole population in a three- to four-year cycle. Humans are infected through inhalation of dust from vole droppings.