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Tick-borne encephalitis is endemic in Europe, in the Far East and in Asia. At present, it is reported regularly in 27 European countries, however with extreme differences in the morbidity rates. For 19 European countries we have reliable data on the TBE incidences since 1976. In these countries, 157,584 TBE cases were registered from 1990 to 2007. If we exclude Russia from this data pool, a total of 50,486 cases remain for Europe (Suss, 2008). In addition to human TBE cases transmitted by tick bites and - more rarely - by milk and milk products, TBE also occurs (more rarely) in dogs, monkeys and horses (Suss et al., 2008b). A steady rise in TBE morbidity was observed over the past 30 years, i. e. 400% from 1976 to 2003 (Suss, 2003; 2008; Randolph, 2004). In a number of "TBE countries" another significant increase was reported from 2004 to 2006. On the other hand, strong fluctuations and a decrease in morbidity have been observed more recently (2007 and 2008) in several European countries. The reasons are unclear (Suss, 2008). It is certain that there are numerous factors which influence these developments. Neglecting the increased awareness of the problem, we can state that almost all social, political, ecological, economic and demographic factors have an impact on the extent of the exposure to tick bites (Suss et al., 2008a). However, in spite of a number of publications on this subject it remains unclear how these many factors interact with each other and how significant they are (Suss and Kahl, 2008). Undoubtedly and supported by the available data, the climate change improves the living conditions of ticks in Europe, especially those of the main vector Ixodes (L) ricinus. This is especially true for an increase in mean temperatures and precipitations, which cause changes in the microclimate that is so important for I. ricinus and other tick species (Gerstengarbe and Werner, 2008). The north- and westward movement of vectors (and pathogens), the increased population density in certain regions, among others caused by an increased availability of hosts and an acceleration of the development cycle, a continued host seeking activity in winter and especially the occurrence of ticks at much higher altitudes in the mountains (meanwhile at up to over 1500 m above sea-level) are measurable factors (Suss et al., 2008b; Dautel et al., 2008; Materna et al., 2008; Gray et al., 2009; Heinz et al., personal commun.). In addition to L ricinus, Dermacentor reticulatus is a good indicator for these changes. The occurrence (or detection?) of newTBE risk areas may be a consequence of these developments. However, science just begins to investigate the molecular epidemiology of TBE virus strains with regard to the geographic distribution of the virus. Although the influence of climate change can be proven reliably, the extent of this influence (e. g. climate change vs. reduction of pollutants in certain regions) is unclear and should be the subject of further investigations

This review presents an overview of the developments in the epidemiology of tick-borne encephalitis (TBE) during 2007 in Europe, the Far East and Asia, as well as some comments interpreting the various developments. The recent TBE situation in 29 European and four non-European countries is shown and discussed. The number of registered TBE cases from 1976 to 2007 in 19 European countries with endemic TBE is presented. Although criteria for TBE reporting vary from one country to another and it is necessary to account for unreported cases, an overall increase of TBE incidence during the last 30 years can clearly be established. Besides changes in climate and weather, a number of additional factors are probably responsible for this rise: increased exposition, partly due to socio-economical and political changes, and other factors that are for the most part unknown. In addition, the immunisation coverage in the population of some of the countries is discussed.

Die Frühsommer-Meningoenzephalitis (FSME) hat seit Mitte der siebziger Jahre des vorigen Jahrhunderts in ganz Europa und Fernost erheblich an Bedeutung gewonnen, die Zahl der registrierten Erkrankungen hat zugenommen und die Risikogebiete haben sich ausgedehnt. Für diese Entwicklung ist eine Reihe von Faktoren verantwortlich zu machen (globale Erwärmung, höhere Aufmerksamkeit, bessere Diagnostik, Änderungen im politischen, sozialen und ökonomischen Bereich). Bei der hohen Qualität und Immunogenität der auf dem Markt befindlichen FSME-Impfstoffe für Kinder und Erwachsene dürfte die Zurückdrängung der FSME heute kein Problem sein. Für eine wissenschaftlich begründete Impfstoffapplikation (Indikationsimpfung) ist die ständige Überwachung der FSME-Risikogebiete und die Aktualisierung der Datenbanken wesentliche Voraussetzung. Die epidemiologischen Daten zur Ausdehnung von Risikogebieten und zum Risikoniveau sind sowohl für Deutschland als auch für die meisten europäischen Länder mit einem FSME-Risiko verfügbar und können für reisemedizinische Zwecke genutzt werden ; The importance of TBE has increased considerably since the mid 70 s in the whole of Europe and Far East. The number of registered clinical cases has risen and risk areas have expanded. For this development a number of factors are responsible ( i. e. global warming, ecological, political, social changes). Because of the high quality and immunogenicity of TBE vaccines available for children and adults TBE should not have to be considered any longer as a problem, subject to the fact that every person at risk has been vaccinated. An important prerequisite for a scientifically based vaccine application are the constant surveillance of TBE risk areas and an actual data base. Epidemiological data with respect to the expansion of risk areas and its level of risk are available covering most European countries with TBE risk and can be made available for medical purposes when travelling.

In the period between 1974 and 2003, the incidence of TBE increased appreciably in most European countries. Numerous factors, including climatic changes, biological (ecological) and non-biological factors, have an influence on the epidemiology of TBE. In addition, a greater awareness and better understanding (of the problem), improvements in diagnosis, an increase in travel, political and associated major social changes have had an impact on epidemiological data banks. We shall succeed in turning back the rising tide only by achieving further progress in the field of risk analysis, and redoubling our efforts in the area of active immunisation. ; Jedes Jahr steigt in Europa die Zahl der gemeldeten FSME-Erkrankungen weiter an. Entsprechend werden immer mehr Gebiete als Risiko- und Hochrisikozonen deklariert. Jeder dritte Erwachsene trägt von einer FSME-Infektion langwierige, manchmal dauerhafte Funk tionsstörungen davon — ganz zu schweigen von den Todesfällen. Raten Sie Ihren Patienten, die in Risikogebieten leben oder dort ihren Urlaub verbringen wollen, deshalb rechtzeitig zur Impfung.

The International Scientific Working Group on Tick-Borne Encephalitis (ISW TBE) held its 13th Annual Meeting in February 2011 to discuss epidemiological developments, news in TBE research, initiatives of the European Union, vaccination-immune response, clinical cases and TBE consequences, awareness of TBE prevention and the role of the ISW TBE to break vaccination fatigue. TBE may be considered a complex system, characterized by an intricate interplay between tick biology and socioeconomic conditions. The same may be said about vaccination behaviour. Thus, although the facts are simple--vaccination is the best prevention--the socioeconomic conditions keep changing, and with them the ability or willingness of people to get vaccinated. The ISW TBE is part of this complex system, and because the world keeps changing--so should the strategies.

Over the past decades, tick-borne encephalitis (TBE), Lyme Borreliosis (LB), and other tick-borne diseases (TBDs) have become a growing public health problem in Europe and other parts of the world. In Europe, 90% to 95% of all tick bite incidences in humans are caused by Ixodes (I) ricinus (in Eastern Europe by persulcatus). Neglecting the large number of unreported cases, 100,000 to 150,000 of these incidences become manifest as LB and between 10,000 and 15,000 as TBE. TBE virus (TBEV) is endemic in regions of 27 European countries and the number of risk areas has increased every year.2 TBEV is also endemic in some parts of Japan, China, and Mongolia. Hence, there are severe health problems for inhabitants and travelers. TBE is predominantly reported in humans and seldom in dogs and horses. Recently, a clinical case of TBE was described in a monkey after natural exposition. The reason for this development is not quite clear, but it can be stated for certain that global warming causes some of these dramatic changes.4 Recent stringent data were discussed in this article. However, there are additional factors to be considered, such as social and political changes in agricultural production and in leisure time and an increase in traveling, which in turn leads to a higher exposition rate.

In Germany, 100-300 autochthonous clinical TBE cases have been recorded annually. There are high-risk areas in Bavaria and Baden-Wuerttemberg and ongoing low-risk areas in Hesse, Thuringia, and the Rhineland-Palatinate and single cases in Saxony. In order to be able to evaluate the epidemiological changes described here, it must be mentioned that a new definition of TBE risk areas was introduced on the district level in 1998 in Germany and in 2001 with the new Infection Protection Act (Infektionsschutzgesetz) which states that TBE is a notifiable disease. This led to the replacement of earlier surveillance systems and to many changes to data collection. In 1998 63 country and town districts were TBE risk areas, in 2001 79 and in 2002 86. There were new risk districts within Bavaria and Baden-Wuerttemberg and outside these regions in Thuringia, Hesse and the Rhineland-Palatinate. An interesting trend was observed in TBE epidemiology. The TBE incidence in Bavaria and Baden-Wuerttemberg has been stable on a high level for years; outside these areas it has steadily been climbing (Odenwald, Thuringia). On the basis of epidemiological data on TBE from the eastern part of Germany since 1960, it is obvious that major changes in virus activity in TBE risk areas also occurred in the past, the explanation of which has remained a matter for speculation. The epidemiological situation in the different risk areas for TBE in Germany was found to vary considerably, if one considers the surveillance data of the last 40 years. 1. Establishment of completely new low-risk areas. 2. Reactivation of formerly active areas with endemic latency. 3. High-risk areas with stable viral activity over long periods. 4. High-risk areas which have expanded and merged with low-risk areas. 5. High-risk areas which have developed into endemic areas or become inactive. High-risk TBE areas from 1960-1975 (i.e. Mecklenburg-Western Pomerania) have since completely disappeared. There were, at the same time, high-risk areas in Thuringia which had only become latent and have now obviously become active again. The Odenwald demonstrated growing virus activity in the 1990s. These changes in TBE activity in German risk areas over more than the last 40 years are presented schematically. This ongoing number of risk areas is certainly linked to the notification obligation and greater public awareness. Nevertheless, any effects of ecological and climatic changes on the natural foci cannot be ruled out nor can changes in human leisure behaviour. Local weather conditions also have a major effect on the TBE incidence. Warm and dry summers may cause low tick activities, rainy summers may lead to low exposure rates of human beings. Even changes in forms of agricultural production prompted by different political structures probably have an impact as do economic constraints which may lead to lower vaccination and higher exposure rates. Regular, systematic virus prevalence measurements from 1997 to 2002 in field-collected ticks in German high-risk areas do not indicate any risk increase nor do they suggest a downward trend. Studies on virus prevalence in questing versus partially engorged ticks indicate that we neither exactly know nor understand the real quantitative relations between the virus and the host. In a first study, virus prevalence in Ixodes ricinus removed from humans was examined. Humans which were exposed in some districts near Passau in Bavaria. In the autumn of 2001, virus prevalence of unengorged free-living nymphs (n = 820) in this area was 0.38 (0.08-1.1)% and of adults (n = 90) 1.17 (0.03-6.38)%. Surprisingly, virus prevalence in partially engorged ticks from the same area collected during the same period was significantly higher (nymphs, n = 86, 6.9% and adults, n = 129, 9.3%). Virus-positive partially engorged ticks were only found in districts known as risk areas. Nucleotide and deduced amino acid sequence data of the PCR products have confirmed the presence of virus prototype Neudoerfl only