[Japanese encephalitis].

Japanese encephalitis is an arboviral disease due to a flavivirus transmitted by a mosquito of the genus Culex. It is a major public health problem in Southeast Asia where it is endemo-epidemic. The socio-economic impact of Japanese encephalitis is great since most cases occur in children and young adults and lead to death in 25 to 30 % and neurological sequelae in survivors. The tendency of Japanese encephalitis to spread geographically and the existence of imported cases are particularly important issues. The clinical features are the same as other viral encephalitis. Suspicion of imported Japanese encephalitis depends on awareness of the epidemiological setting (return from endemic areas). Diagnosis must be confirmed by serology using ELISA capture method to detect anti-viral antibodies in blood and cerebrospinal fluid. Unlike herpes encephalitis, there is currently no specific treatment for Japanese encephalitis. Only preventive measures can be effective against infection. At the present time the most widely used vaccine is Biken's lyophilized vaccine produced from a reference strain (Nakayama strain), but its high cost prevents mass vaccination in endemic areas. Recent progress in molecular biology has raised hope for the discovery of a genetically engineered vaccine to improve overall protection against Japanese encephalitis.