Surveillance of Japanese encephalitis cases in Thailand.

This surveillance study reveal the incidence of Japanese encephalitis cases throughout the year with an increase during the rainy-seasons. JEV attacks all ages, but with a high incidence found in age group between 8 to 14 years determined from the studies in 1974, 1975 and 1976 and records of distribution in 40 provinces of Thailand. The severity of infection is high to warrant virus surveillance by the Ministry of public Health.