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As a result of a longitudinal study of the Puumala hantavirus (PUUV) in the experimentally infected bank voles (Myodes glareolus), we revealed three groups of the voles differing in the immunoreactivity and viral antigen concentration in the organs. The close correlation between these parameters suggested the existence of various mechanisms of the hantavirus persistence in the host.

The findings suggest that there are natural foci of hantavirus infection in the Tambov Region. There is evidence that Dobrava/Belgrade hantavirus (DOB-Aa) was a leading etiological agent in the outbreak of the disease in the winter of 2006-2007. Epidemiological analysis showed that the outbreak of hemorrhagic fever with renal syndrome (HFRS) afflicted the region during November to April, by reaching its peak in January (52.2%). Among the patients with HFRS, rural dwellers were 91%. People were infected with the virus mainly by taking care of domestic animals (97.2%). The reservoir of the virus and the source of its human infection in the outbreak was a field mouse, its western subspecies Apodemus agrarius agrarius, which was absolutely dominated among all the virus carriers.

The specific features of hantavirus infection in naturally infected bank voles (Clethrionomys glareolus), the principal host of hantavirus of the serotype Puumala, were studied during long-term observation of individually marked animals in the active focus of hemorrhagic fever with renal syndrome (HFRS) in the south of Udmurtia. The infection time in the bank voles was defined by paired serum seroconversion tests. In the natural focus, hantavirus was shown to cause asymptomatic persistent infection in the bank voles with the body's peak accumulation of the virus and its environmental discharge within the first month of infection. In this period the animals present the greatest epidemic and epizootic hazards. Hantavirus infection has no negative impact on the viability of bank voles.

Lungs of 3159 animals of the forest complex from 90 areas of 30 administrative districts of Tyumen Province were examined by enzyme immunoassays for antigen of hemorrhagic fever with renal syndrome (HFRS) during 5 years, 1985-1989. The antigen of HERS virus was detected in the lungs of mammals of 8 species: Clethrionomys glareolus and Cl. rutilus, Siberian and Arctic lemmings (first findings in the world), M. oeconomus, field mouse, common and pygmy shrews. Nearly all the findings refer to the subzone of southern taiga and adjacent areas of subtaiga subzone where Cl. glareolus is the main reservoir of infection and Cl. rutilus an additional one. In the tundra zone, Siberian lemming is the main reservoir of infection and Arctic lemming an additional one. No natural foci of HFRS were found in forest steppe and forest tundra zones. In the subzone of the northern and middle taiga, the antigen was found only on 4 occasions: 3 in common shrews and one in Cl. glareolus (near the town of Khanty-Mansisk). An irregular annual infection rate with HFRS virus was observed in Cl. glareolus as well as its decline from spring to autumn. It cannot be ruled out that lemmings are carriers of a distinct HFRS virus serotype.