VORONEZH, Russia, Dec. 27 (UPI) -- The Voronezh region of central Russia is once again seeing an epidemic of hemorrhagic fever, this time affecting the kidneys.

Fifty people in the Voronezh region have contracted the illness, Russia's Itar-Tass reported Wednesday.

The press service of the regional Health Department said that the disease has been registered in the region's five areas as well as Voronezh.

A large increase in the population or rodents, which proved to be 10 times more than previous years, preceded this latest outbreak. The increase in rodents is connected to unseasonably warm weather in the region this winter.

This form of hemorrhagic fever, a disease that causes bleeding, isn't rare in the Voronezh region. There was an epidemic in the 1960s as well as another five years ago, when 50 people were reported to have contracted the fever.