The changing incidence of tickborne encephalitis in Europe

The recorded incidence of tickborne encephalitis (TBE) in Europe and Russia has changed over the past two decades, but the geographical pattern of change is heterogeneous (1) (see figure). The most dramatic changes of all were the sudden increases (2- to 30-fold) in 1992-3 in Latvia, Lithuania, Poland and Belarus, with marked but lesser increases in Estonia, Germany, Slovakia, and the Czech Republic. TBE cases have increased steadily since the mid-1970s in Russia, and since the mid-1980s in Switzerland, Sweden, and Finland. Since 1997, the first cases have appeared in Norway (2). Along the southern edge of the virus's range, in Slovenia, Croatia and Hungary, incidence has fluctuated and shown no consistent trend apart from signs of decreasing over the past 4-5 years. In Austria, the only country with extensive systematic vaccination coverage, TBE incidence has decreased progressively since the early 1980s.