Risk of Contracting TBE
Exact calculations of the risk of infection and the resulting morbidity rate are extremely difficult, as tick bites are often not noticed.
Virus transmission may be estimated to occur in one of about 3–200 tick bites in areas endemic for TBE, depending on the prevalence of TBE virus in ticks.
In the different endemic areas of TBE, the risk for infection of humans after a single tick bite varies between 1:200 and 1:1000.
According to estimations by Roggendorf et al., the risk of infection in German endemic areas is 1:900. In a study of endemic areas in Sweden, the annual incidence (new infections within the studied population) was found to be 1.2 to 2.4%, the risk of infection following a tick bite was estimated to be about 1:600.