Japanese encephalitis

Japanese encephalitis (JE), formerly known as Japanese B encephalitis to distinguish it from Economo's A encephalitis—is a disease caused by the mosquito-borne Japanese encephalitis virus (JEV).

The Japanese encephalitis virus (JEV) itself is a virus from the family Flaviviridae, part of the Japanese encephalitis serocomplex of 9 genetically and antigenically related viruses, some which are particularly severe in horses, and four known to infect humans including West Nile virus.

Domestic pigs and wild birds (especially herons) are reservoirs of the virus; transmission to humans may cause severe symptoms. Amongst the most important vectors of this disease are the mosquitoes Culex tritaeniorhynchus and Culex vishnui. This disease is most prevalent in Southeast Asia and East Asia.

Signs and symptoms

Japanese encephalitis has an incubation period of 5 to 15 days and the vast majority of infections are asymptomatic: only 1 in 250 infections develop into encephalitis.

Severe rigors may mark the onset of this disease in humans. Fever, headache and malaise are other non-specific symptoms of this disease which may last for a period of between 1 and 6 days. Signs which develop during the acute encephalitic stage include neck rigidity, cachexia, hemiparesis, convulsions and a raised body temperature between 38–41 °C (100.4–105.8 °F). Mental retardation is usually developed.