Myyräkuume cases ease in Central Ostrobothnia after record year

Central Ostrobothnia has recorded the highest per capita rate of Puumala virus infections in Finland this year, though the outbreak is now subsiding, according to Yle.

The region has confirmed 42 cases in the first half of 2026, double the typical annual count of around 20. While severe cases requiring hospital treatment for kidney symptoms have declined since the peak in late autumn and winter, infections remain elevated compared to a normal spring.

Nationally, North Savo has reported the most cases in absolute numbers, with nearly 80 confirmed. Helsinki, by contrast, has seen just 10 cases this year, down from over 50 in 2025.

Fluctuations in bank vole populations drive the variation in infections. Populations have surged in North Ostrobothnia and southern Kainuu, with a potential peak expected in late autumn. In eastern Finland, Central Finland, and South Ostrobothnia, vole numbers have collapsed from last year’s levels.

The Puumala virus, which causes nephropathia epidemica—commonly known as myyräkuume—spreads through dust from vole excretions, leading to high fever, severe pain, and often kidney symptoms. There is no specific treatment for the viral illness.