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Japanese encephalitis is a serious infection caused by a virus that is transmitted to humans by the bite of infected mosquitoes. Most Japanese encephalitis virus infections are asymptomatic. In symptomatic cases, severity varies. Symptoms include fever, headache, convulsions, focal neurological symptoms (eg. disturbances in speech and walking depressed level of consciousness and coma). Permanent brain damage is common in people who survive a severe infection. Approximately 25% of severe clinical cases die.^7,31

Transmission³¹
Various species of mosquitoes transmit the virus to humans. Mosquitoes become infective after biting infected pigs or birds. There is no person-to-person transmission.

Geographical distribution^7,31
Infection is endemic in a number of countries in Far East and South East Asia . It occurs occasionally in far north Queensland , Australia .

See Japanese encephalitis virus distribution map

Risk for travellers^7,31,31a
The risk of infection with Japanese encephalitis for travellers to Southeast Asia is low but varies with the season of travel (risk is higher during the wet season), the type of accommodation, the area of travel (risk is higher in rural and agricultural areas) the type of activities undertaken (eg. outdoor activities especially in the twilight period) and the duration of exposure. Short stays in good hotels with limited likelihood of mosquito bites result in very low levels of risk. In contrast, campers in rural areas during the wet season may be at high risk.

Precautions and prevention⁷

• Vaccination. New generation vaccines with low risk of adverse effects are now available in Australia. The vaccine is highly effective and recommended for:
  - travellers to rural areas of Asia if they intend to stay there for at least 4 weeks. JE vaccination should also be considered for shorter term travellers, particularly if travelling in the wet season and/or there is considerable outdoor activity and/or the level of accommodation is not mosquito proof.
  - expatriates spending a year or more in Asia (excluding Singapore ) even in urban areas.
  - Travellers intending to stay a month or more in Papua New Guinea, particularly if the travel is during the wet season. (See your doctor)
• Avoiding mosquito bites is as important as being immunised. Please follow precautions under Insect avoidance.

(Please read the Disclaimer before using the ABC Guide to Travel Health).

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