Risks of Japanese encephalitis

Learn what the risks of Japanese encephalitis are and who is most at risk.

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What are the risks of being infected with Japanese encephalitis?

Japanese encephalitis occurs in:

  • almost all Asian countries
  • parts of the western Pacific

It is mainly a threat in rural agricultural areas where there is widespread irrigation (artificial watering of crops). This includes areas with rice fields.

It usually spreads during the summer and fall in temperate regions (areas with 4 seasons), such as:

  • China
  • Japan
  • Korea

Japanese encephalitis can spread year-round in tropical and subtropical areas of Southeast Asia, such as:

  • Vietnam
  • Thailand
  • Malaysia
  • Indonesia
  • Singapore

Mosquitoes that carry Japanese encephalitis bite mainly from sunset to sunrise.

Who is most at risk?

The risk to most travellers is low, especially for those staying in cities.

Travellers to countries where Japanese encephalitis is common have a higher risk of infection if they are:

  • visiting rural and agriculture areas, especially if they stay over a longer period of time (a month or more)
  • doing outdoor activities, such as:
    • hiking
    • cycling
    • camping
    • fieldwork

The disease is fatal in about 20% to 30% of severe cases. Infants and the elderly who are infected are more likely to develop severe disease.

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