Puumala virus

PUUV · HFRS

Overview

Puumala virus is the most common hantavirus in Europe and the principal cause of hemorrhagic fever with renal syndrome (HFRS) in the region — a milder form sometimes called nephropathia epidemica. The reservoir is the bank vole (Myodes glareolus), which experiences cyclical population peaks every 3–4 years that drive corresponding spikes in human cases. Most infections produce fever, headache, abdominal pain, and acute kidney injury that typically resolves with supportive care, including dialysis when needed.

Discovery

Puumala virus was identified in 1980 by Markus Brummer-Korvenkontio and colleagues at the University of Helsinki, who isolated antigen-positive material from bank voles trapped near the municipality of Puumala in eastern Finland. The clinical syndrome — "nephropathia epidemica" — had been recognised in Scandinavian medical literature since the 1930s as a distinct, milder form of HFRS, but its viral cause was unproven until reagents from the newly-isolated Hantaan virus enabled cross-serology that linked the European disease to the broader hantavirus family.

Rodent reservoir

The bank vole (Myodes glareolus) is a small reddish-brown rodent ubiquitous across deciduous and mixed forests of Eurasia, from Ireland to Lake Baikal. Population density is strongly driven by mast years — heavy seed production by beech, oak, and spruce — which trigger autumn-to-spring vole population booms. These cyclical irruptions, occurring every three to four years across much of central Europe, produce corresponding spikes in human Puumala incidence the following spring and summer. Bank voles infected with Puumala virus shed virus persistently without illness, primarily in saliva, urine, and droppings.

Transmission

Human Puumala infection occurs through inhalation of aerosolized bank-vole excreta, almost always in indoor or semi-enclosed spaces with autumn or winter rodent activity — summer cabins, woodsheds, garages, storage outbuildings, agricultural barns. Forestry work and the post-winter cleaning of seasonal cabins are recognised high-exposure activities. Person-to-person transmission of Puumala virus has not been documented; case clustering reflects shared exposure to contaminated environments, not human-to-human spread.

Clinical course

Puumala virus disease (nephropathia epidemica) is the mildest classical HFRS. After a 2–4 week incubation, patients develop abrupt fever, headache, severe lower-back and abdominal pain, transient blurred vision, and proteinuria. Acute kidney injury follows, often requiring brief dialysis. The clinical course unfolds over roughly two weeks with full recovery in the vast majority of cases. Severe haemorrhage and circulatory collapse — the hallmarks of Hantaan-virus HFRS in Asia — are uncommon in Puumala infection.

Diagnosis

Diagnosis is straightforward in endemic regions: IgM and IgG serology by ELISA or immunofluorescence, with high sensitivity by the time of clinical presentation. PCR is available at reference labs but rarely needed clinically. Routine labs show thrombocytopenia, leukocytosis with left shift, elevated creatinine and CRP, proteinuria, and microscopic haematuria. Any patient in Scandinavia, Germany, Belgium, France, or central Europe with acute fever and rapidly rising creatinine should be considered for Puumala virus testing, especially during autumn–winter and mast years.

Treatment & prognosis

Treatment is entirely supportive: analgesia, IV fluid resuscitation as tolerated, and renal replacement therapy (typically haemodialysis) for the 5–10% of patients who develop oliguric AKI. Most patients recover fully within 2–3 weeks with no long-term sequelae; rare cases have been associated with persistent hypertension or modest reductions in glomerular filtration. Ribavirin and other antivirals have not been shown to provide benefit for Puumala virus infection given the typically mild course.

Prevention

Prevention emphasises rodent exclusion from cabins, sheds, and storage outbuildings — sealing openings ¼-inch or larger, eliminating food and shelter sources. When opening a vole-affected building after winter, ventilate for at least 30 minutes before entry, use an FFP2/N95 respirator, wet down droppings with a 1:10 bleach-water solution rather than sweeping, and double-bag waste. Public-health agencies in Finland, Germany, and Belgium issue seasonal advisories during bank-vole peak years to alert at-risk rural and forestry populations.

Tracked countries

Live risk index and news for countries where Puumala virus is documented or surveilled.

Notable outbreaks

1. 2005
   Germany

   Major Puumala virus year with more than 400 cases reported to RKI, particularly in Baden-Württemberg.

2. 2007–2008
   Finland and central Europe

   Major Puumala epidemic linked to a bank-vole population peak; thousands of confirmed cases across the region.

3. 2012
   Germany

   Notable case spike (~2,800 reported cases), particularly in Baden-Württemberg and Bavaria.

4. 2021
   Belgium and the Netherlands

   Western European bank-vole peak year producing a cluster of cases.

References & primary sources

• ECDC — Puumala Virus Factsheet
• Robert Koch-Institut — SurvStat (Germany)
• THL — Finnish Institute for Health and Welfare
• Sciensano — Hantavirus Surveillance (Belgium)

Other hantavirus strains