Encephalitis

What is encephalitis?

Swelling of the brain. In South and South-East Asia it is mostly caused by the Japanese encephalitis virus, carried by mosquitoes.

Signs

Most infections cause mild fever and headache, or nothing. A few become severe: high fever, stiff neck, confusion, fits, weak or paralysed limbs, and coma.

How it spreads

Through bites from Culex mosquitoes that picked up the virus from pigs or wading birds, mainly in farming areas. It does not pass between people.

How to protect yourself

Safe, effective vaccines exist; WHO recommends them where the disease is common. Also avoid mosquito bites with repellent, long sleeves, coils and nets.

Get medical help

Brain swelling is an emergency. Go to hospital at once for high fever with stiff neck, confusion, fits or unusual sleepiness, especially in a child.

In Dooram's words, from the World Health Organization. Source: WHO fact sheet: Japanese encephalitis, read 8 October 2026. General information, not medical advice.