[Viral encephalitis].
Viral encephalitis presents with fever, headache, focal and generalized neurologic symptoms and signs, seizures, and CSF pleocytosis. Herpes simplex Virus (HSV) 1 and arboviruses (flaviruses) are the most common causes of encephalitis in Switzerland. The initial work-up in a suspected encephalitis includes CSF analysis, EEG, and brain CT or MRI. The identification of the responsible agent usually occurs with polymerase chain reaction or serology. The differential diagnosis to other infectious and non-infectious acute CNS-disorders may initially be arduous. A specific treatment is possible only in encephalitis caused by viruses of the herpes group. Active immunization should be considered in subjects at high risk for tick-borne encephalitis. With early treatment the prognosis may be satisfactory also in HSV encephalitis.