Japanese encephalitis is an infection of the brain caused by Japanese encephalitis virus (JEV) primarily transmitted by certain mosquitoes in Asia and Western Pacific.
Japanese encephalitis (or Japanese B encephalitis) is a viral disease spread by infected mosquitoes. The risk of disease is greatest in parts of Southern and Eastern Asia, the Indian subcontinent, Micronesia and Melanesia. The risk of disease is greatest in rural areas, changes with the season and varies by region. JEV is considered the leading cause of viral encephalitis in Asia.
People traveling to an endemic area should consult a travel clinic about their destination to see if they should receive the JE vaccine.
Japanese encephalitis is caused by a virus belonging to the family Flaviviridae. It is spread by the bite of certain kinds of mosquitoes.
The disease is not spread from person to person.
In its early stages, Japanese encephalitis is similar to a flu-like illness. Symptoms appear five to 15 days after infection and may include:
- headache
- fever
- nausea
- vomiting
- diarrhea
- confusion, and other changes in behaviour
- seizures
Many people infected with Japanese encephalitis virus have no or mild symptoms.
Travellers of all ages are at risk of getting the disease if bitten by mosquitoes. Older travellers who get infected often develop symptoms of confusion or changes in behaviour. In about one out of every 200 cases, the illness progresses to swelling of the brain. More than half of these cases end in permanent disability or death.
Infection during the first six months of pregnancy may result in infection of the baby and miscarriage.
Detection of antibodies in the blood serum is the most common way of diagnosing Japanese encephalitis.
There is currently no drug treatment for the disease. People with Japanese encephalitis should receive supportive care, including treatment of symptoms.
Talk to a health care provider, or call 811 for advice, if you feel unwell within 15 days of a mosquito bite in an endemic area.
The best way to prevent this disease is to avoid being bitten by mosquitoes. There are several steps you can take to prevent mosquito bites while still enjoying time outdoors.
- If you are taking part in outdoor activities between dusk and dawn, use insect repellent on all exposed skin (one containing at least 30% concentration of DEET). Follow label instructions carefully.
- Wear light-coloured, loose, clothing with long sleeves, pants and socks.
- Sleep in places with screened windows and doors, or places which have air conditioning (so you can close the windows and doors).
- Sleep under an intact, small-mesh mosquito net which has been sprayed with a permethrin (insecticide) preparation. Tuck mosquito net under mattress before nightfall. The mosquito net is particularly important if it is not possible to stop mosquitoes from entering your room.
- Use insecticidal spray indoors in the evening.
- Use non-perfumed cosmetics and toiletries. Mosquitoes are attracted to scented products.
- Travel vaccines, like the Japanese encephalitis vaccine, are recommended for people travelling to or working in some countries. It is important to talk to your health care provider or visit a travel clinic at least 6 to 8 weeks before you travel.
For more information on the Japanese encephalitis vaccine, visit
HealthLinkBC.
