Cases of plague due to infection with Yersinia pestis have been seen in approximately 40 patients each year, especially in rural areas. The most common source of human plague is contact with and consumption of the marmot (Marmota sibirica). Moreover, the great gerbil (Rhombomys opimus) and the Mongolian gerbil (Meriones unguiculatus) are suspected of being enzootic reservoirs.