Learn About Japanese Encephalitis Virus JEV


Japanese encephalitis virus JEV is the most important cause of viral encephalitis in Asia. It 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.

JE primarily affects children. Most adults in endemic countries have natural immunity after childhood infection, but individuals of any age may be affected.

Signs and Symptoms
  • Less than 1% of people infected with the Japanese encephalitis (JE) virus develop clinical illness.
  • In persons who develop symptoms, the incubation period (time from infection until illness) is typically 5-15 days.
  • Initial symptoms often include fever, headache, and vomiting.
  • Mental status changes, neurologic symptoms, weakness, and movement disorders might develop over the next few days.
  • Seizures are common, especially among children.

To reduce the risk for JE, all travelers to Japanese encephalitis-endemic areas should take precautions to avoid mosquito bites. Travelers spending extensive time in JE endemic areas are recommended to get vaccinated before travel.

  • Wear neutral-color (beige, light grey) clothing. If possible, wear long-sleeved, light-weight garments.
  • If available, pre-soak or spray outer layer clothing and gear with permethrin.
  • Apply sunscreen first followed by the repellent (preferably 20 minutes later).
  • Use a repellent containing 20%-30% DEET or 20% Picaridin on exposed skin. Re-apply according to the manufacturer’s directions.
  • Get rid of water containers around dwellings and ensure that door and window screens work properly.

* All content published is for general information purposes only and should not be construed as medical advice.