Occurrence of childhood encephalitis: a population-based study.

The occurrence of childhood encephalitis was evaluated in a population-based study in an area with no arboviral infections. Ninety-five children were treated for encephalitis during 1973 to 1987, giving an annual incidence of 8.8/100,000 children younger than 16 years of age (95% confidence interval, 6.7 to 10.1). Based on virologic and serologic studies the most common etiologic agents were varicella (24 cases), mumps (8), herpes simplex (7) and measles (4). The etiology remained unknown in 37 children. No cases of encephalitis caused by mumps, measles or rubella were found in the population after 1982, when vaccination against these viruses was introduced.