Japanese Encephalitis is a potentially fatal brain infection caused by a virus spread by mosquito bites. Some people are infected without severe illness and are not diagnosed, but of those who become ill, recovery may be associated with neurological and psychiatric complications. Whilst it was originally discovered in Japan, the risk season there is very brief, in the middle of summer. In more southern, equatorial countries it is an all year round risk. The Culex mosquito that spreads the disease is mainly active in rural areas, and travellers most at risk are those spending extended time outside cities and towns. Ducks and pigs are involved in the virus’ life cycle, and farming areas, especially rice paddies (where there is abundant water on the ground), are higher risk destinations
The infection is confined to Asia, spreading from Pakistan in the west, across to Papua New Guinea in the east, and as far north as Russia and Japan. Presently, there is a high risk of the disease in the popular tourist destination of Bali.
Is there a Japanese Encephalitis vaccine?
First line protection is based around mosquito bite prevention, such as DEET based insect repellents on exposed skin, permethrin impregnation of clothing and mosquito nets, mosquito coils and screened accommodation. For higher risk travel eg a month or more in rural areas, 2 safe and effective Japanese Encephalitis vaccines are available – a single vaccine that provides at least 5 years’ protection, or a slightly less expensive 2 dose schedule providing protection for at least a year. Protection against the disease is not fully achieved until around 7 days after vaccination.