Tick-borne encephalitis in the Tyrol (Austria): Changes in incidence and endemicity 2000–2006

All cases of tick-borne encephalitis (TBE), which were recorded in the Tyrol (Austria) between 2000 and 2006, were investigated, in order to detect changes in incidence and endemicity, to identify particular risk groups, and to evaluate the indication for vaccination. Patients, who presented with an acute febrile illness, positive anti-TBE IgM and/or seroconversion, an at least two-fold increase of anti-TBE IgG or confirmation of TBE by the reference centre were questioned about previous vaccination, circumstances and possible places of infection, outdoor activities, and changes in their personal risk of infection. Sixty-one cases of TBE (among them 2 imported cases) were identified between January 2000 and December 2006, yielding an average annual incidence of 5.8 cases for 2000–2004 and 16 cases for 2005–2006. This increase was largely due to patients >60 years of age who had never been vaccinated against TBE. In 2005–2006, there was an increase in case fatality rates, admission to intensive care units, and duration of intensive care. During 2005 and 2006, new endemic areas were identified upstream the valleys of Inn and Isel, and there is evidence of a rise of new foci within the known endemic areas. Possible reasons for this development include climatic factors like a lower saturation deficit in August than in comparative years. Vaccination strategies should be focused on patients >60 years of age without previous vaccination who are convinced that sticking to the habits of a lifetime offers sufficient protection against TBE.