Travellers are advised to prevent mosquito bites at all times. This very serious disease attacks the brain and can be fatal. There are recurring epidemics are Sub-Saharan Africa, Mongolia, Vietnam, the Amazon area in Brazil, northern India and Nepal. A fever, severe headache, sensitivity to light and neck stiffness which prevents forward bending of the head are the first symptoms. There may also be purple patches on the skin.
Death can occur within a few hours, so urgent medical treatment is required.
Trekkers to rural areas of Nepal should be particularly careful, as the disease is spread by close contact with people who carry it in their throats and noses, spread it through coughs and sneezes and may not be aware that they are carriers. Lodges in the hills where travellers spend the night are prime spots for the spread of infection. Treatment is large doses of penicillin given intravenously, or chloramphenicol injections. They infect certain varieties of freshwater snails found in rivers, streams, lakes and particularly behind dams. The worms multiply and are eventually discharged into the water.