Japanese Encephalitis

Japanese encephalitis is a virus that affects the brain and can be fatal. Not everyone experiences Japanese encephalitis symptoms, but they can be severe, such as seizures. Transmission of Japanese encephalitis can only occur if you are bitten by mosquitoes in risk areas. Prevention includes a vaccine that protects nine out of ten people.

Risk areas
South East Asia, the Pacific islands and the Far East
Survival rate
Infections a year
Infections in children
75% of cases
People at highest risk
People working and living in rural areas, children

01. Transmission of Japanese encephalitis

Being bitten by an infected mosquito is the only cause of Japanese encephalitis, and you can protect yourself by getting vaccinated.

You cannot catch the disease by having contact with an infected person.

Mosquitoes can become carriers of the disease after sucking the blood of an infected human or animal, particularly pigs and birds.

This is also why Japanese encephalitis transmission is more common in people working or living near farms, rice paddies or marshes in risk areas.

It is hard to pinpoint specific seasons when the risk of Japanese encephalitis is higher, as seasonal patterns vary within individual countries and from year to year.

In the subtropics and tropics, transmission can occur year-round. However, travelling during rainy seasons and early dry seasons in risk areas should be avoided if possible.

02. Risk areas for Japanese encephalitis

Japanese encephalitis is not common in travellers, with just one in a million travellers becoming infected with the virus each year.

However, this should not discourage you from ensuring you are protected, as the disease can be fatal, if you become infected.

Japanese encephalitis is usually found in rural areas of Southeast Asia, the Pacific islands and the Far East, but it can be present in cities as well.

Despite its name, Japanese encephalitis is now rare in Japan as a result of effective vaccination programmes.

Travellers are most at risk of Japanese encephalitis transmission when visiting:

  • China

  • Myanmar

  • Thailand

  • Vietnam

  • Cambodia

  • Laos

  • Nepal

  • India

  • Philippines

  • Sri Lanka

  • Malaysia

  • Indonesia

It is important to know that outbreaks can occur anywhere in the world. This means that the Japanese encephalitis risk areas change.

Check if the country you are travelling to has a risk of Japanese encephalitis through the search bar below.

03. Symptoms of Japanese encephalitis

Japanese encephalitis symptoms do not occur in most people infected by the virus.

Those that do experience mild Japanese encephalitis symptoms recover very quickly and often mistake the disease for the flu.

One in every 250 people, who become infected with the Japanese encephalitis virus, develop more severe symptoms.

This can happen if prompt Japanese encephalitis treatment is not received, and the virus is allowed to spread.

This usually happens five to 15 days after infection, and is known as the Japanese encephalitis incubation period.

Symptoms of Japanese encephalitis can include:

  • fever

  • seizures

  • neck stiffness

  • confusion

  • speech problems

  • body tremors

  • muscle weakness

  • paralysis

Up to one in every three people, who develop serious Japanese encephalitis symptoms, die as a result of the infection. Those who survive, see a slow improvement of symptoms, and it can take several months to recover fully.

04. Diagnosis of Japanese encephalitis

Japanese encephalitis diagnosis usually involves testing your blood or sometimes fluid from your spine or brain.

Tests can confirm a Japanese encephalitis infection in most people between four and seven days after symptoms begin.

If you have been travelling in a Japanese encephalitis risk area and feel unwell, you should see a doctor and tell them about your recent travels to help them make a japanese encephalitis diagnosis.  

If you are still travelling and become ill, it is important you seek a diagnosis as soon as possible.

It is a good idea to keep a list of important telephone numbers with you when travelling abroad, including who you can contact for medical treatment.

05. Treatment of Japanese encephalitis

If your Japanese encephalitis symptoms are mild, you will usually require no Japanese encephalitis treatment, and you will probably not even realise that you had the disease.

If you develop serious symptoms, you will usually need to stay in hospital. In hospital you will be given fluids, oxygen and medication through a small tube in your vein, known as an IV.

Treatment of Japanese encephalitis usually involves keeping you safe and comfortable as your body tries to fight off the infection. For example, if you are having seizures, it is important you do not fall or get injured.

Up to half of the people who survive the disease are left with permanent brain damage and long-term problems, such as tremors and muscle twitches, personality changes, learning difficulties and paralysis.

Ongoing treatment and support may include physiotherapy, mobility aids, therapy and specialist help in school or work. However, some people are not ever able to return to their everyday lives.

06. Prevention of Japanese encephalitis

There are many things you can do to decrease your risk of Japanese encephalitis transmission.

Japanese encephalitis prevention includes avoiding mosquito bites. This is crucial, as this is the only way you can become infected with the Japanese encephalitis virus.

There are things you can do to limit your chances of being bitten, but it is impossible to guarantee that you will not be bitten in a risk area. This is why it is important to check if you need the Japanese encephalitis vaccine.

If you need to get vaccinated for Japanese encephalitis, you can book a vaccination appointment online today.

If you are unsure if the Japanese encephalitis vaccine is right for you, book a free telephone consultation to speak to one of our prescribing nurses, who can give you a personal recommendation based on your health and travel plans.

For effective Japanese encephalitis prevention while travelling in Japanese encephalitis risk areas, it is recommended that you:

  • check if you need the Japanese encephalitis vaccine

  • learn about Japanese encephalitis so you can spot signs

  • use mosquito nets

  • wear loose clothing that covers your arms and legs

  • use insect repellent containing 50% DEET

  • spray your sleeping area with insecticide

  • avoid camping near water, rice paddies and farms

Content reviewed by

Anne Marie Major, Independent Nurse Prescriber
24 June 2019