Japanese Encephalitis: Causes and How It Spreads

Primary cause

Japanese encephalitis is caused by a virus that is found in Asia and the western Pacific.

The virus belongs to a group of viruses called flaviviruses. Other flaviviruses cause similar disease, including West Nile virus, St. Louis encephalitis virus, tick-borne encephalitis virus, and Powassan virus.

How it spreads

• Japanese encephalitis virus circulates in the environment between mosquitoes (primarily Culex species) and other animals, namely wading birds and pigs.
• People become infected with the virus when mosquitoes feed on other infected animals and then bite people.
• People are considered dead-end hosts meaning they do not develop high enough levels of virus in their bloodstream and cannot pass the virus on to other biting mosquitoes.
  • The virus is not transmitted from person-to-person, except rarely by blood transfusion.
  • Because the virus can be transmitted through blood, persons who were recently diagnosed with Japanese encephalitis virus infection should not donate blood and bone marrow for 120 days following infection.
• The virus is not transmitted directly from person-to-person and is not spread:
  • Through coughing, sneezing, or touching
  • By touching live animals
  • From handling live or dead infected animals. Avoid bare-handed contact when handling any dead animal. If you are disposing of a dead animal, use gloves or double plastic bags to place the carcass in a garbage can.
  • Through eating infected animals. Always follow instructions for fully cooking meat.
• Prevent getting sick with Japanese encephalitis by preventing mosquito bites and getting vaccinated before traveling, if vaccination is recommended for you.