TBE foci in Switzerland

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To give information about the situation in Switzerland and especially in the canton Thurgau. Tick-borne encephalitis (TBE) in Switzerland has to be reported to official bodies, such as the Cantonal Office of Health and the Swiss Federal Office of Public Health. The registered cases are published weekly in the Bulletin of the Swiss Federal Office of Public Health. A map with geographical sites of infection has been published by the Swiss Federal Office of Public Health from time to time. In addition we collect epidemiological data in our diagnostic setting servicing part of eastern Switzerland. The situation of every patient diagnosed in our laboratory is followed up by a questionnaire. Some data derive from an epidemiological study conducted by Baumberger et al. (1996) and from another study conducted in the principality of Liechtenstein ( Krech et al., 1992). The data of a more recent publication are also included (Schwanda et al., 2000). More historical data are taken from Krech (1980). Recently, the global positioning system (GPS) connected to a laptop computer containing a geographical map on CD-ROM was used for better determination of possible TBE microfoci. TBE is endemic in areas of northern Switzerland and the principality of Liechtenstein. The number of reported new infections in Switzerland per year ranges between 60 and 120 cases, most of them with neurological manifestations. This represents an incidence of 0.5–1.5 per 100,000 inhabitants per year. In the last 10 years a prominent increase of the number of reported cases occurred in Switzerland, namely from 30–70 cases per year to 60–120 cases per year. This increase was mainly caused by the emergence of TBE in the cantons of Thurgau, Aargau and St. Gallen, all localised in the north-eastern part of Switzerland. The canton Thurgau became the most dangerous region in Switzerland for TBE during the last ten years. Besides the known endemic areas of the regions of Schaffhausen, Thun and Biel-Ins, a number of additional foci have been detected during the last 20 years. These are situated, for instance, around the lake of Zurich or in the region of Chur. In the canton Thurgau, new cases could be located east of the formerly known foci. Besides the larger epidemic areas known there are several TBE virus microfoci in Switzerland and more microfoci are still recognized. Despite active vaccination of persons at risk the incidence of reported TBE cases has increased during the last 20 years, now being between 60 and 120 cases per year, some of them with a severe and prolonged course. No TBE foci have been recognized in western und southern Switzerland so far. From our observations we have got the impression that real new TBE foci are emerging in some regions of eastern Switzerland.