[Early summer meningoencephalitis. Extension of the endemic area to mid-Hessia]

Tick-borne encephalitis (TBE) is the most severe arbovirus disease transmitted 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 with TBE acquired in Middle-Hessen between 1994 and 1997 (2 in 1997). After repeated CSF and serum testing the TBE-specific antibodies were found in all 4 cases. In one case there was also evidence for a prior infection with borrelia burgdorferi. The results of the initial CSF-analysis were atypical in 2 cases (high cell count of 136 cells/mm3, total protein up to 1.5 g/l). The endemic region for TBE has expanded in northern direction into Middle-Hessen, a region in which Lyme borreliosis is also endemic. Thus, true double infections are possible. This and the initially frequently atypical CSF-findings make the differential diagnosis difficult. Therefore, repetitive CSF and blood examinations are recommended.