DISTRIBUTION OF CALIFORNIA SEROGROUP VIRU SES (BUNYAVIRIDAE, BUNYAVIRUS) IN NORTHERN RUSSIA

The study was carried out in 1983-1991 and covered a territory of abou t 10x10(6) km(2) in various physico-geographic areas (East Fennoscandi a. Northern Russian Plain, West Siberia, Central Siberia. North-Easter n Siberia, and Northern Pacific Region) ill the Arctic, Subarctic. Nor thern-Central-Southern taiga, forest-steppe, and steppe in Northern Ru ssia. A total of 251 strains were isolated from 1391,900 mosquitoes, i dentified as the California group snowshoe hare (83), Inkoo (44), and Tahyna (2) viruses; 122 strains were not completely identified. Some o f the strains with uncommon antigenic composition can be natural reass ortants. Fifty-two percent of strains were isolated from Aedes communi s and the associate species of mosquitoes, other hosts were A. excruci ans (8%), A. cantans (6.25%), A. flavescens (6.25%), A. ciprius (6.25% ), A. punctor (4.5%), A. vexans (4.5%), A. cataphylla (3.6%), A. nigri pes (3.6%), and A. hexodontus (2.6%). The infection rate of mosquitoes was 0.009% in the tundra, 0.012% in forest-tundra, 0.01% in Northern taiga, 0.02% in Central taiga, 0.017% in Southern taiga, 0.026% in for est-steppe, and 0.097% in steppe. The epidemic season is one month in the tundra (from the beginning of July till the beginning of August), two mouths in Northern taiga (July-August), and three months in Centra l taiga (from the second half or June till the beginning of September) . The highest infection rate of mosquitoes was observed at the end of the epidemic season in ail regions. SSH strains prevailed to the East from the Enisei river, whereas to the West and in the Sub-arctic regio ns INK virus predominated, SSH being rare; in the taiga the distributi on was quite the opposite. TAH virus was virtually absent. Human morbi dity was observed in all territories studied. The immune stratum of ad ult population is about 30% in the tundra and forest-tundra and about 50% in Northern and Central taiga.