Everything about Japanese Encephalitis

Japanese Encephalitis

  • It is a viral disease that infects animals and humans.
  • In humans, it can cause inflammation of membrane around the brain.
  • Japanese encephalitis virus (JEV) is the most important cause of viral encephalitis in Asia.
  • JEV is a mosquito-borne flavivirus and belongs to the same genus as dengue, yellow fever and West Nile viruses.
  • The first case of Japanese encephalitis viral disease (JE) was documented in 1871 in Japan.

Signs and symptoms

  • Most JEV infections are mild (fever and headache) or without apparent symptoms, but approximately 1 in 250 infections results in severe clinical illness.
  • Severe disease is characterised by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis and ultimately death.
  • Acute encephalitis syndrome (AES) is a clinical condition caused by infection with JEV or other infectious and noninfectious causes.


  • JEV is transmitted to humans through bites from infected mosquitoes of the Culex species (mainly Culex tritaeniorhynchus).
  • Domestic pigs and wild birds are reservoirs of the virus.
  • In most temperate areas of Asia, JEV is transmitted mainly during the warm season, when large epidemics occur.
  • In the tropics and subtropics, transmission can occur year-round but often intensifies during the rainy season.