Japanese encephalitis virus infection

Abstract

Japanese encephalitis (JE) is a viral encephalitis caused by Japanese encephalitis virus (JEV), a single stranded positive sense RNA virus of the genus Flavivirus. The reservoir of JEV is wild birds and pigs; it is spread to humans by mosquitoes. There are approximately 68,000 cases and 15,000 deaths per year. JE is endemic to South and Southeast Asia where 2.5 billion people live. Although most of this population are exposed to JEV, only a minority develop JE. JE is a disease of children and the adult population is immune as a result of childhood exposure. The factors that determine whether or not disease develops relate largely to the host immune response and are still being actively investigated. Patients with JE develop a febrile illness followed by the onset of headache, vomiting, clouding of consciousness and possibly seizures. A wide range of neurological abnormalities are possible; for example focal upper motor neuron lesions, acute flaccid paralysis and extrapyramidal features. There are no proven effective therapies and treatment is supportive; however, JE can be prevented by vaccination. A number of vaccines are available including both live attenuated and inactivated cell culture derived vaccines.