Tick borne encephalitis in Middle-Hessen. Expansion of the endemic area

Tick-borne encephalitis (TBE) is the most severe arbovirus disease transmit ted by ticks. The mortality of the central European form is 0.7-2%. Active immunisation is recommended for endemic regions. We report on 4 patients wi th TBE aquired in Middle-Hessen between 1994 and 1997 (2 in 1997). After re peated CSF and serum testing the TBE-specific antibodies were found in all 4 cases. In one case there was also evidence fora prior infection with borr elia burgdorferi. The results of the initial CSF-analysis were atypical in 2 cases (high cell count of 136 cells/mm(3), total protein up to 1.5 g/l). The endemic region for TBE has expanded in northern direction into Middle-H essen, a region in which Lyme borreliosis is also endemic. Thus, true doubl e infections are possible. This and the initially frequently atypical CSF-f indings make the differential diagnosis difficult. Therefore, repetitive CS F and blood examinations are recommended.