Japanese encephalitis virus (JEV) is a flavivirus related to dengue, yellow fever, and West Nile virus that can be spread by some (but not all) types of mosquitoes.
Japanese encephalitis (JE) is a rare, severe manifestation of infection with JEV, occurring in many parts of Southeast Asia and China. In recent years the disease has extended beyond its traditional boundaries with cases occurring in eastern Indonesia, Papua New Guinea, the Torres Strait, and mainland Australia.
Signs and symptoms
The majority of people (about 99%) infected with JEV have no symptoms or mild symptoms. Those that do develop symptoms may experience a fever and headache, or abdominal pain and vomiting in children. Severe disease may be characterised by an acute encephalitis (inflammation of the brain), with sudden onset of high fever and chills, severe headache, neck stiffness, disorientation, convulsions, paralysis, and coma. Of these severe cases, approximately one-third die, and one-third are left with permanent disabilities.
JEV can only be spread by the bite of an infected mosquito. Mosquitoes become infected after they bite infected pigs or wading birds. After a person is bitten by an infected mosquito, it usually takes 5 to 15 days for the first symptoms to appear. JEV does not spread directly between people.
There is no specific treatment. Treatment usually involves management of the symptoms.
JEV infection is preventable through vaccination and avoidance of mosquito bites.
The Communicable Disease Network Australia has prioritised vaccination for people who are at high-risk of exposure to JEV.
Read further advice from the Australian Government Department of Health on the Japanese encephalitis virus (JEV) vaccines, including eligibility criteria.
Vaccination is also recommended if you are travelling to Asia and the Torres Strait region of Australia and will be:
- travelling in rural areas
- undertaking certain activities with increased risk of exposure
- spending a month or more in the region.
Personal protection measures can reduce the risk of you and your family getting bitten by mosquitoes. These include:
- Avoiding mosquitoes when they are most active, particularly at dusk and dawn.
- Covering up with light-coloured, loose-fitting clothing with long sleeves, long trousers, and socks, and covered footwear when outside.
- Using an effective insect repellent on exposed skin and reapply within a few hours, following the manufacturer’s instructions. The best mosquito repellents contain Diethyl Toluamide (DEET) or Picaridin.
- Repellents containing less than 10 per cent DEET or picaridin are considered safe for children, however the use of topical repellents is not recommended for infants under 3 months of age. It is best to use physical barriers—such as nets on prams and cots—to protect infants less than 3 months of age. Young children should not apply repellents themselves. Repellents should be applied to the hands of a carer first, and then applied evenly to the child’s exposed skin.
- Using insecticide sprays or vapour dispensing units (indoors) or mosquito coils (outdoors) to repel mosquitoes.
- Ensuring that flyscreens in your home, tent or caravan are in good condition so mosquitoes cannot enter.
- Using mosquito-proof tents when camping.
- Using mosquito nets when sleeping unless accommodation is air conditioned or has mosquito screens on doors and windows.
To stop mosquitoes breeding on your property, remove any standing water or water-holding containers or empty and wipe out the container, wherever possible.
Help and assistance
If you are in an emergency situation call 000
Get qualified health advice 24/7 for the cost of a local call, 13 HEALTH (13 43 25 84)
For further information, please contact your local doctor, community health centre or nearest public health unit. Travel vaccines need to be considered in the context of your specific travel itinerary. Immunisation needs should be discussed with your doctor or travel medical centre at least 6 weeks before you travel. For further advice on travel vaccinations, visit the Australian Government’s Smart Traveller website.
- Having a vaccination what to expect fact sheet
- Barmah Forest virus fact sheet
- Kunjin virus disease fact sheet
- Ross River virus fact sheet
- Mosquito-borne disease prevention when travelling
- Mosquito-borne diseases after a storm, flood or cyclone
- Japanese encephalitis | The Australian Immunisation Handbook
Australian Technical Advisory Group on Immunisation (ATAGI). (2018). Australian Immunisation Handbook, Australian Government Department of Health, Canberra
Department of Health. (2022). Japanese Encephalitis
Heymann, D.L. (2015). Control of Communicable Diseases Manual, 20th edition. Washington, DC: American Public Health Association.
World Health Organization. (2015). Japanese Encephalitis Fact Sheet