Tick-borne encephalitis.

In middle and eastern European countries, tick-borne encephalitis (TBE) is one of the most important human infections of the central nervous system. TBE virus (TBEV) is mainly transmitted by tick bites and rarely by unpasteurized milk. In European countries, TBE presents as meningitis in about 50% of patients, as meningoencephalitis in 40%, and as meningoencephalomyelitis in 10%. The severity of TBE increases with age; in children and adolescents, meningitis is the predominant form of the disease. The long-term prognosis is unfavorable in about 40% to 50% of patients who sustain sequelae for months to years, mainly in terms of pareses, ataxia, and other gait disturbances. No specific treatment for TBE is known. It can be successfully prevented by active immunization.