[Viral encephalitis, early summer meningoencephalitis].

Encephalitis is an unusual manifestation of viral infections. Encephalitis manifests with fever, headache and an altered level of consciousness. To identify an etiologic diagnosis, epidemiologic data (season, prevalent diseases, travel, exposure and animal contacts) may be helpful, whereas clinical findings mostly are nonspecific. The cerebrospinal fluid analysis shows a moderate pleocytosis with a slightly increased protein concentration. With PCR, the ability to diagnose CNS viral infections has improved, particularly for herpes simplex and enteroviral infections. Effective therapy is available only for a limited number of viral infections. Some cases of encephalitis can be reliably prevented by vaccination (measles, mumps, TBE, rabies). Tick-borne encephalitis (TBE), which is of particular interest in Switzerland, is described in detail.