[Long-term study of natural foci of tick-borne encephalitis in the District of Olomouc].

The incidence of natural foci of tick-borne encephalitis in the Olomouc district has been characterized as general. This finding is based on analyses of results of earlier reports and results of serological blood tests of 397 small mammals from localities where probably transmission of the infection to humans occurred. The incidence almost corresponds to the incidence of the tick Ixodes ricinus. It has a long-lasting and also cumulative character; the number of reported cases from the main focal areas is proportional to the frequency of localities infestated with Ixodes ricinus ticks, assuming an approximately equal number of visitors in the woods of the district.