Where is this disease found?

The infection is found all over Asia - from India to Japan. In most of these areas, the infection is only transmitted in certain seasons. In an area with a temperate climate, most infections take place in summer and autumn. In other regions, the risk exists throughout the year. The presence of the virus varies by region, country and year. About 50,000 cases of Japanese encephalitis are reported annually.

What are the symptoms of this disease?

In most people, the disease is asymptomatic or has the same symptoms as a mild flu, such as fever, headache and muscle pain. In severe cases, symptoms of inflammation of the membranes of the brain (meninges) can occur together with headache and vomiting, followed by drowsiness, coma and epileptic seizures. Potentially fatal paralysis and breathing difficulties can also occur.

How is this disease contracted?

The virus is transmitted by mosquitoes. In high-risk areas, the number of infections each year is up to 10 cases per 10,000 people. Children are more likely to contract it before the age of fifteen. Nearly all adults have enough antibodies to withstand the virus. However, in some regions an increase in incidence among elderly people has been noted.

What action should you should take?

For most travellers to Asia the chances of contracting this disease are relatively small. Those who live or stay permanently in rural areas during the peak season for infection are at the highest risk. Such people should be vaccinated against the disease. Vaccination provides eighty to ninety per cent protection against Japanese encephalitis.

Recommended preventive measures include:

• Plan any travel to rural areas of Asia outside the high-risk season.
• Use mosquito repellents (preferably containing DEET) and mosquito nets.
• Wear clothing that covers the entire body.
• Get vaccinated before starting travelling.