[Tick-borne encephalitis in a northern zone of coniferous and broad-leaved forests of a focal region of the Amur River basin].

The geographical variability of the population of tick-borne encephalitis (TBE) virus in the northern part of the zone of combined coniferous and broad-leaved forests was established; this variability was manifested by higher virulence and homogeneity of TBE virus strains, as shown in experiments on white mice receiving the virus extraneurally, in comparison with the southern part of the zone and by higher virus carriership of the ticks Ixodes persulcatus. With the epizootic situation remaining tense and the danger of TBE virus infection still present, TBE morbidity and mortality rates decreased in the years of the construction of the Baikal-Amur Railroad, which was due to greater attention given to measures for the prophylaxis of TBE during this period.