Japanese Encephalitis is caused by a virus passed on through infected mosquitos. The virus is transmitted to humans through pigs and wading birds via a mosquito bite. It is mainly a problem in rural farming areas and occurs throughout Southeast Asia and the Far East. It is usually a mild illness but can have serious complications leading to inflammation of the brain (encephalitis) which can cause permanent brain damage, and in some cases be fatal. Vaccination against Japanese Encepahlitis is usually advised for travellers who stay longer than a month during the rainy seasons in rural areas of high risk countries. If you are travelling abroad, you can visit the UK NHS website Fitfortravel or the National Travel Health Network and Centre to find out if immunisation against hepatitis B is recommended.