Japanese encephalitis

Japanese encephalitis is an infection of the brain caused by a virus spread through mosquito bites. It is found in parts of Asia and the western Pacific, especially in rural farming areas. Most people who are infected have no symptoms or only a mild illness, but a small number develop serious brain inflammation.

Last updated Nov 9, 2026

What it is

There is no specific treatment. People with severe illness are cared for in hospital.

A vaccine is recommended for some travellers, depending on where they go, for how long and what they will do. Avoiding mosquito bites also helps.

Common signs

  • Usually no symptoms
  • High temperature and headache
  • Feeling sick and vomiting
  • In severe cases: confusion, seizures, a stiff neck and weakness

How it is usually diagnosed

  • Blood tests
  • Lumbar puncture
  • Brain scans

Records worth keeping

Keeping these together makes each appointment easier, especially when you see a new doctor:

  • Vaccination dates
  • Travel history
  • Hospital discharge letters

Questions to ask your doctor

  • Do I need the vaccine for my trip?
  • How long before travel should I be vaccinated?
  • How can I avoid mosquito bites?

When to get help right away

Call 112 or go to the nearest emergency department if you have:

  • Fever with confusion, seizures, a stiff neck or drowsiness after travel to an affected area: call 112

This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.

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