Writing in the International Journal of Health Geographics, the scientists report that an epidemic of the viral disease nephropathia epidemica (or NE) can be traced to increases in the vole population brought on by hotter summers, milder winters and increased production of the tree seeds that form the core of the vole diet.
"This animal-borne disease, scarcely known before 1990, has been increasing in incidence in Belgium with a cyclic pattern, reaching epidemic proportions since 2005," said Jan Clement of the department of microbiology and immunology at Belgium's University of Leuven, the study's lead author. "The fact that the growing combined effect of hotter summer and autumn seasons is matched by the growth of NE in recent years means this epidemic can be considered an effect of global warming."
The study notes that of the 2,200 cases since Clement began charting them in 1985, 828 (or about 37 percent) occurred in just the last three years,. The epidemic has also crossed Belgium's borders, popping up in neighboring countries such as France, Germany, The Netherlands and Luxembourg.
Nephropathia epidemica is actually caused by infection with the Puumala virus, or PUUV, which is carried and spread by the bank vole, which ranges throughout Europe. The study authors suggest that warmer weather has caused an increase in the principle staples of the vole diet: plant seeds from oak and beech trees. The warm summers also improve the chances that people will visit the rural areas and forests where the voles live, which is how the disease is transmitted from rodent to human.
The Puumala virus is a hantavirus, which can cause hemorrhagic fevers and severe flu-like symptoms that often require Intensive Care treatment. In some rare cases, the disease can be fatal, causing internal bleeding. As Clement said in a press release announcing the study's findings: "In 1997, more than 9,000 people in the Russian republic of Bashkortostan contracted the disease, of which 34 cases were fatal."
The entire article is available here for free: http://www.ij-healthgeographics.com/content/8/1/1