Tick-borne encephalitis (TBE) is endemic in parts of many European countries including most countries involved in the EpiNorth collaboration. TBE is emerging or re-emerging in new areas. The epidemiology of TBE in Europe varies between low-risk areas such as Norway, Denmark, Sweden, and Finland, and high-risk areas such as Estonia, Latvia, and Lithuania. The backgroud for endemicity is not established and estimating the risk of infection difficult because tick bites are often not noticed.
A TBE endemic area is defined as an area with TBE-virus circulation between ticks and vertebrate hosts as determined by the detection of TBE-virus or the demonstration of autochthonous infections in humans or animals within the last twenty years. The development of a TBE natural foci depends on different factors including the dynamics of infected ticks and their hosts, population density, susceptibility of individual hosts, proportion of immune population, properties of the biotype, temperature, climate change and sociological changes.
Mobility within a country as well as tourism to foreign countries fuels the infection. Outdoor activities, recreation and tourist activities involving contact with nature increase the risk of tick bites. The main tourist season corresponds to the main period for tick activity from April to October. The number of travel-associated TBE cases is probably vastly underestimated in part because many travellers are unware of the TBE risk when visiting endemic areas in the region.
Prevention is important because there is no effective treatment for TBE. Avoiding tick bites is the best prevention. Vaccination for both adults and children residing in or travelling to highly endemic areas should be considered and national health authorities should consider general vaccination of the population in highly endemic areas.
EpiNorth journal is offering in this issue a series of articles from Belarus, Estonia, Denmark, and Lithuania addressing the epidemiology of tick-borne diseases and possible factors that have contributed to the recent increase of these infections. A more general overview of tick-borne encephalitis in Europe and neighbouring countries is described by J.Süss et al. in a publication from Eurosurveillance.
EpiNorth c/o Department of Infectious Disease Epidemiology, Norwegian Institute of Public Health, P.O.Box 4404 Nydalen, N-0403 Oslo, Norway. Tel: + 47 21 07 67 45, Fax: + 47 21 07 65 13, E-mail: