日本腦炎係感染日本腦炎病毒引起的急性腦膜腦炎，日本腦炎病毒的感染大部分為無症狀感染，少部分輕微病例會產生頭痛、發燒或無菌性腦膜炎等症狀，嚴重者則出現頭痛、高燒、腦膜刺激、昏迷、痙攣等症狀，最後導致精神、神經性後遺症。本文針對此一疾病作簡單的綜論讓讀者更能了解此疾病。

Japanese encephalitis is an infection of the brain caused by a virus. The virus is transmitted to humans by mosquitoes. 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. Illness usually begins with sudden onset of fever with gastrointestinal symptoms and headache. Mental status or behavioral changes, focal neurologic deficits, generalized weakness, and movement disorders may develop over the next few days. Seizures are very common among children. Milder forms of disease such as aseptic meningitis or fever with headache can occur, more commonly among adults.