THE 2002-2021 EPIDEMIC SITUATION FOR TICK-BORNE ENCEPHALITIS AND LYME DISEASE IN THE NORTH-WESTERN FEDERAL DISTRICT OF THE RUSSIAN FEDERATION

Abstract The study objective was to reveal 2002-2021 trends in tick-borne encephalitis (TBE) and Lyme disease (LD) epidemic processes in the North-Western Federal District of the Russian Federation (NWFD). In NWFD during the analyzed period more than 1.1 million patients sought medical help due to tick bites (14% of all cases registered nation-wide), and the long-term average tick bite incidence rate in NWFD exceeded the nation-wide range (409.5 and 280.7, respectively). In NWFD the highest long-term average tick bite incidence rates were recorded in Vologda Oblast, Pskov Oblast and Novgorod Oblast. The tick bite incidence rate tended to grow in NWFD, as well as nation-wide. The rise of tick bite incidence rate was statistically significant in the Komi Republic, Kaliningrad Oblast and Arkhangelsk Oblast. In 2002-2021 more than 6 thousand of TBE cases were registered in NWFD (11% of all cases registered nation-wide), and the long-term average incidence rate of TBE in NWFD exceeded that nation-wide (2.3 and 2.0, respectively). The Republic of Karelia, Arkhangelsk Oblast and Vologda Oblast were three NWFD subjects with high TBE epidemical hazards. The TBE incidence rate in the analyzed period tended to decrease both in NWFD and nation-wide. A statistically significant decrease in TBE incidence rate was revealed in St. Petersburg, the Republic of Karelia, Novgorod Oblast and Leningrad Oblast. About 22 thousand of LD cases were reported in NWFD during the period analyzed (15% of all LD cases in the Russian Federation), and the long-term average incidence rate of LD in NWFD exceeded that for nation-wide level (7.9 and 4.9, respectively). Vologda Oblast, Kaliningrad Oblast and Pskov Oblast were the three NWFD subjects with high epidemical hazards in terms of LD incidence rate, which tended to decrease both in NWFD and nation-wide. The decrease in LD incidence rate was statistically significant in Vologda, Kaliningrad, Novgorod, Leningrad and Pskov Oblasts, as well as in St. Petersburg. In Vologda Oblast, Arkhangelsk Oblast, as well as the Komi Republic there were long-range undulations of TBE and LD incidence rates over the period analyzed. In the Komi Republic, in contrast to other NWFD subjects and nation-wide data there was an uptrend in incidence rates of both TBE and LD.