Japanese encephalitis (JE) is an infection of the brain caused by the Japanese encephalitis virus (JEV).[3] While most infections result in little or no symptoms, occasional inflammation of the brain occurs.[3] In these cases, symptoms may include headache, vomiting, fever, confusion and seizures.[1] This occurs about 5 to 15 days after infection.[1]

JEV is generally spread by mosquitoes, specifically those of the Culex type.[2] Pigs and wild birds serve as a reservoir for the virus.[2] The disease mostly occurs outside of cities.[2] Diagnosis is based on blood or cerebrospinal fluid testing.[2]

Prevention is generally with the Japanese encephalitis vaccine, which is both safe and effective.[2] Other measures include avoiding mosquito bites.[2] Once infected, there is no specific treatment, with care being supportive.[1] This is generally carried out in hospital.[1] Permanent problems occur in up to half of people who recover from JE.[2]

The disease occurs in Southeast Asia and the Western Pacific.[2] About 3 billion people live in areas where the disease occurs.[2] About 68,000 symptomatic cases occur a year, with about 17,000 deaths.[2] Often, cases occur in outbreaks.[2] The disease was first described in Japan in 1871.[2] Despite its name, the disease is now relatively rare in Japan as a result of large-scale immunisation efforts.[4]