Puumala virus is a species of hantavirus

Hantavirus

Hantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent waste products...

. Humans infected with the virus may develop a haemorrhagic fever with renal syndrome (HFRS) known as nephropathia epidemica

Nephropathia epidemica

Nephropathia epidemica is a type of viral haemorrhagic fever with renal syndrome caused by the Puumala virus. The incubation period is three weeks. Nephropathia epidemica has a sudden onset with fever, abdominal pain, headache, back pain and gastrointestinal symptoms. More severe symptoms include...

. Puumala virus HFRS is lethal in a small percentage of cases.

Puumala virus is named after a municipality

Municipality

A municipality is essentially an urban administrative division having corporate status and usually powers of self-government. It can also be used to mean the governing body of a municipality. A municipality is a general-purpose administrative subdivision, as opposed to a special-purpose district...

 in Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

. The virus is found predominantly in Scandinavia

Scandinavia

Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

 and Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, although it has also been reported elsewhere in Northern Europe and Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. Because the bank vole

Bank Vole

The bank vole is a small vole with red-brown fur and some grey patches, with a tail about half as long as its body. A rodent, it lives in woodland areas and is around in length. The bank vole is found in western Europe and northern Asia...

 (Myodes glareolus) acts as a reservoir

Natural reservoir

Natural reservoir or nidus, refers to the long-term host of the pathogen of an infectious disease. It is often the case that hosts do not get the disease carried by the pathogen or it is carried as a subclinical infection and so asymptomatic and non-lethal...

 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.
It has been theorized that Puumala virus, unlike other members of the genus Hantavirus

Hantavirus

Hantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent waste products...

, may also have lethal effects on its rodent host.

Puumala virus was discovered and named in 1980 by researchers in Finland.