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Japanese encephalitis

Learn more about the condition

It’s important to make sure you’re up-to-date with your vaccinations before you set off on your travels. Here we explain Japanese encephalitis, what it is, where it can be contracted and how you can help reduce your risk when travelling.

What is Japanese encephalitis and how do you catch it?

Spread through mosquito bites, Japanese encephalitis is a rare but serious viral brain infection. The virus starts with a mosquito biting an infected pig or bird, then going on to bite a human, transmitting the disease. The infection can’t be passed from person to person.

The virus is most common in South East Asia, the Pacific Islands and the Far East. The risk for most travellers is low, especially for short stay travellers. Those at higher risk are travellers to rural areas and those staying near to rice fields or pig farms for one month or longer.

Signs and symptoms

Japanese encephalitis doesn’t always present symptoms, but if they do occur they're usually mild and flu-like.

One in every 250 people develop more severe symptoms. This usually takes place five to 15 days after infection when it spreads to the brain. Severe Japanese encephalitis symptoms can include:

  • High temperature (fever)
  • Seizures
  • Stiff neck
  • Confusion
  • Inability to speak
  • Uncontrollable shaking of body parts
  • Muscle weakness or paralysis

As these can be signs of many different diseases, you should seek immediate medical attention if you become unwell with flu-like symptoms and any of the symptoms listed whilst away or on your return.


The virus has no cure, however treatment can be given to aid the body as it fights off the infection. Symptoms usually require hospital treatments such as fluids, oxygen and medication.


The most effective way to prevent Japanese encephalitis is by means of vaccination.

It’s also important to protect against being bitten by mosquitos. To help prevent bites, you should:

  • Use mosquito nets
  • Wear long sleeves and trousers that are loose-fitting
  • Spray rooms with insecticide
  • Wear insect repellent


The vaccination, given as an injection, is administered in two doses for protection. The second dose can either be given 28 days after the first, or, when time is short, seven days after the first (an ‘accelerated’ schedule). The two doses should be completed at least seven days before your departure.

If you’re at higher risk of the disease, you should consider being vaccinated. It’s particularly important if:

  • You’re travelling to a high-risk country during rainy season
  • You’re visiting rural areas such as rice fields, marshlands or animal farms
  • You’re likely to be doing activities that could increase your risk, such as cycling or camping

How long does the Japanese encephalitis vaccination last?

If you’re at prolonged risk of infection, you should have a booster injection 12 to 24 months after the initial vaccination.

Our service​​​​​​​

For a free assessment, expert advice and vaccinations, book an appointment online with Boots Travel Vaccinations and Health Advice Service. Ideally, this should be six to eight weeks before departure, but it’s never too late to seek advice if you're leaving sooner.