Japanese encephalitis 

Introduction 

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Japanese encephalitis is a type of viral brain infection spread through mosquito bites. It’s common in rural areas throughout Southeast Asia, the Pacific islands and the Far East.

The virus is found in pigs and birds, and passed to mosquitoes that bite the infected animals. It’s more common in rural areas where there are pig farms and rice fields. It cannot be spread from human to human.

Read more about the causes of Japanese encephalitis.

Most people infected by the Japanese encephalitis virus do not develop any symptoms, or they get only mild, flu-like symptoms.

However, around one person in 250 infected by the virus has serious and severe symptoms, including:

  • being sick
  • seizures (fits)
  • headache
  • mental confusion

In serious cases, the virus can also cause swelling inside the brain (encephalitis), leading to increased pressure in the brain. This can cause permanent brain damage. Japanese encephalitis can be fatal in around one in three people who develop these serious symptoms.

Read more about the symptoms of Japanese encephalitis.

Treatment

There is currently no cure for Japanese encephalitis so treatment involves supporting the functions of the body as it tries to fight off the infection. This will usually involve admission to hospital.

A medication called mannitol can be used to reduce pressure inside the brain, which can sometimes prevent permanent brain damage.

Read more about the treatment of Japanese encephalitis.

Who is affected?

It’s rare for travellers from outside the region to be affected by Japanese encephalitis. It is estimated that only one in 1 million travellers will develop Japanese encephalitis in any year.

People who live and work in rural areas in parts of the world where the condition is widespread are most at risk. Around 9 out of 10 cases involve children under the age of 15 years.

There are an estimated 70,000 new cases every year, half of which occur in China.

Vaccination

Two vaccines are available for Japanese encephalitis. Vaccination is normally recommended if:

  • You are planning to spend a month or longer in a high-risk country during the rainy season.
  • You are planning to visit any rural areas in high-risk countries, even if only for a short time.
  • You will be taking part in any activities that may increase your risk of becoming infected, such as visiting rice fields or pig farms, cycling or camping.

You will normally have to pay for the vaccine, which costs around £150 for the complete course.

Read more about vaccines for Japanese encephalitis.




Page last reviewed: 01/05/2012

Next review due: 01/05/2014

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Comments

The 3 comments posted are personal views. Any information they give has not been checked and may not be accurate.

willt1985 said on 15 April 2013

If you read the article it ways that "Japanese encephalitis can be fatal in around one in three people who develop these serious symptoms."
So it is 1 in 3 people from the 1 in 250 who develop serious side effects that die.

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Skachbow said on 05 November 2012

The same thing struck me - these statements contradict each other:'Most people who are infected by the Japanese encephalitis virus do not develop any symptoms, or they get only mild, flu-like symptoms.
However, around one person in 250 infected by the virus has serious and severe symptoms...Around one in three cases of encephalitis is fatal.'
which is true? or do you mean that 1 in 3 of those who develop symptoms?.....
I'd really appreciate an answer to this - it would affect what decision I make re immunisation....

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User281147 said on 25 June 2009

This article states that "In most cases the illness is mild", however goes on to say that up to 60% of people develop serious inflammation of the brain, which can lead to permanent brain damage or death.

Can you clarify if this is a mild or serious illness?

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