Background. In the pre-elimination era malaria was endemic in most of Europe. In the middle of 20th century all species of malaria were eliminated, and vivax malaria was the last to disappear. Since then, short-living episodes of autochthonous transmission following importation of P.vivax have been documented in a number of European countries, but Russia was the most affected. From 1997 to 2010, more than 500 autochthonous cases were recorded in European Russia. Aims. We investigated the variations of favorability of weather conditions in different parts of European Russia in order to assess their role in malaria re-introduction. Methods. Summer temperatures have been analyzed for 9 geographical points of various climatic zones in East European plain for 51 years up to 2010. The analysis was based on Moshkovsky's method. Each summer season was classified upon its favorability to vivax malaria transmission into 4 groups, from "absolutely unfavorable" to "particularly favorable". Results. During this period the favorability of weather conditions increased, which was particularly marked at the latitudes 52-56°N. For instance, in Moscow before 1984 unfavorable seasons predominated and transmission was impossible during 3 summers. After this point transmission was possible every year, and favorable seasons predominated. Weather conditions were particularly favorable in 1972,1981,1988,1989,1995,1999, 2002, 2007, 2010. During 5 out of those 9 summers autochthonous transmission actually occurred. Conclusions. Since mid-1980s receptivity to malaria increased due to a more favorable combination of temperatures during summers. Average daily temperatures (ADTs) during the first half of June are the most important. If, as it often happens, ADTs drop below +16°C for a week or so during this period, probability of autochthonous transmission during the rest of summer lessens very considerably. This may be used for a short-term forecast of malaria situation.
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