Cases of nephropathia epidemica — a kidney illness caused by a virus carried by bank voles — have doubled in Western Europe over the past 20 years, according to a study summary published by the European Commission’s Science for Environment Policy news alert service.
Nephropathia epidemica is caused by the Puumala virus, which is hosted by the bank vole, a small rodent native to Europe, the summary said.
People are usually infected when they inhale virus particles from the saliva, urine or faeces of infected voles during outdoor work or recreation.
The analysis used monthly records of registered nephropathia epidemica cases from health institutes in Belgium, France, Germany and the Netherlands between 2004 and 2012.
Researchers combined these case records with local information on climate and land cover — such as temperature, rainfall, snow and frost days, vegetation growth and the amount of suitable vole habitat — to model how cases varied over time and place.
Two hotspots linked to forest habitat
The results found “a lot of variation” in case levels across Western Europe and identified two areas where case numbers were consistently higher — one in south-western and central Germany, and another spanning southern Belgium and north-eastern France, the summary said.
Where these hotspots appeared was mostly linked to land-cover factors, including the presence of mixed or broad-leaved forest, which is the bank vole’s preferred habitat.
Climate conditions tended to affect how intense outbreaks became, with the study identifying triggers including mild winters in the year before illness onset and “optimum” summer temperatures two years earlier.
The researchers also reported limits in comparing data across countries because reporting areas differed in size, and because many cases were assigned to a person’s home region rather than where infection was likely to have occurred, often during woodland activities.
The study was published in "Environmental Health Perspectives" in 2025 by Erazo and colleagues.
