What is it: Japanese encephalitis (JE) is a disease that is spread to humans by infected mosquitoes in Asia. It is one of a group of mosquito-borne virus diseases that can affect the central nervous system and cause severe complications and even death. It is a seasonal disease that usually occurs in the summer and fall in temperate regions of China, Japan, and Korea. In other places, disease patterns vary with rainy seasons and irrigation practices.

How do I get it: JE virus is transmitted chiefly by mosquitoes that live in rural rice-growing and pig-farming regions.

What happens if I get it: symptoms usually appear 6-8 days after the bite of an infected mosquito. Most infected persons develop mild symptoms or no symptoms at all. In people who develop a more severe disease, Japanese encephalitis usually starts as a flu-like illness, with fever, chills, tiredness, headache, nausea, and vomiting. Confusion and agitation can also occur in the early stage. The illness can progress to a serious infection of the brain (encephalitis) and can be fatal in 30% of cases. Among the survivors, another 30% will have serous brain damage, including paralysis.

Diagnose and treatment: diagnosis is based on tests of blood or spinal fluid. There is no specific treatment for Japanese encephalitis. A vaccine is licensed for use in travellers whose itineraries might put them at risk for Japanese encephalitis. All travellers should take the usual precautions to avoid mosquito bites to prevent Japanese encephalitis and other mosquito-borne diseases.

How can I avoid contractingJapanese encephalitis: avoid being bitten by mosquitoes. The mosquitoes that transmit Japanese encephalitis feed mainly outside during the cooler hours at dusk and dawn. Travellers should minimize outdoor activities at these times, use mosquito repellent on exposed skin, and stay in air-conditioned or well-screened rooms. Travellers to rural areas should use a bed net and aerosol room insecticides.