Occurrence of TBE in areas previously considered being non-endemic: Scandinavian data generate an international study by the International Scientific Working Group for TBE (ISW-TBE)

Tick-borne encephalitis virus (TBEV) has been endemic in many countries in central, northern and eastern Europe. More than 3000 human cases are reported annually, the Baltic states included. TBEV causes CNS infections presented as meningitis or meningoencephalitis with or without myelitis. The case fatality rate in Europe is approximately 0.5 %, and Lip to 40 % of the patients are left with long-lasting sequelae. The endemicity of TBE in Sweden has been stable over the years but during the last decade several new foci have been discovered. In Norway the first verified cases of TBE have now been found. The reason for this changing epidemiology of TBE is discussed.