Health topics

Encephalitis, viral

Ducks in a rice field WHO/Kimberley Fox

Viral encephalitis is inflammation of the brain, caused by any one of a number of viruses. Symptoms include high fever, headache, sensitivity to light, stiff neck and back, vomiting, confusion and, in severe cases, seizures, paralysis and coma. Infants and elderly people are particularly at risk of severe illness.

Japanese encephalitis (JE) virus, transmitted by mosquitoes in a cycle with water birds and sometimes pigs, is the leading cause of viral encephalitis in Asia. JE is endemic in parts of China, India, the Republic of Korea, Japan, the Russian Federation, islands in the Torres Strait of Australia, Nepal, Thailand, Viet Nam, Cambodia, the Lao People's Democratic Republic, the Philippines, Papua New Guinea, Taiwan, Indonesia, Malaysia, and Sri Lanka.

There is no JE-specific therapy other than supportive care. Most infections result in mild symptoms or no symptoms at all. However, around 1 in 300 infections results in symptomatic illness, which is characterized by a flu-like illness with sudden onset of fever, chills, headache, tiredness, nausea, and vomiting. The illness can progress to encephalitis (infection of the brain) and can be fatal in 30% of cases.