The influence of meteorological conditions of the preceding winter on the incidences of tick-borne encephalitis and Lyme borreliosis in the Czech Republic

Data on tick-borne encephalitis (TBE: 1995–2004, 4122 cases) and Lyme borreliosis (LB: 1999–2004, 7391 cases) occurring in the Czech Republic in the territory of Bohemia were extracted from the database EPIDAT (National Institute of Public Health, Prague). The relationship of the incidence of these diseases to meteorological characteristics of the preceding winter was examined. Included were data from 22 meteorological stations distributed over the territory of Bohemia in areas of high TBE and LB incidence (from the database of the Czech Hydrometeorological Institute, Prague). Nineteen factors characterizing the severity of winter as a whole were examined. The closest correlation (statistically not significant) was between the incidence of TBE and the frost index, followed by the minimum winter temperature during the preceding winter season. Several other comparisons revealed similar correlation coefficients slightly below the limit of significance, nevertheless, even they also support the finding that the severity of winter influences TBE incidence in the following season. The occurrence of LB correlated in similar, not fully significant manner. The most distinct results were achieved with the number of days of thaw and the number of ice days. For both diseases, the meteorological parameters indicating the severity of winter are inversely proportional.