Japanese Encephalitis: How It Spreads, Prevention, Symptoms, And Options For Treatment

Japanese Encephalitis is a mosquito-borne virus that is of the Flavivirus genus. The virus is related to a number of other infectious viral diseases associated with mosquitoes, including yellow fever, the West Nile virus and dengue. Once infected, a patient can develop a condition known as viral encephalitis, referring to swelling in their brains. The condition is quite rare and can become fatal in some cases. No cure is available, but symptomatic treatments are available to ease the symptoms until the patient recovers from the infection.

In this guide, we’ll cover all of the most essential information related to the Japanese Encephalitis Virus, often referred to as JE or JEV. We will share information about the signs and symptoms associated with the viral infection, how the disease is diagnosed, and also consider both preventative and treatment measures that can be put into place to avoid fatal complications.

What Is Japanese Encephalitis?

Japanese Encephalitis is a viral disease. The disease is caused by a virus that infects the human body. Once infected, the virus starts to grow and multiply in the infected person’s body, eventually leading to the development of unpleasant symptoms – when symptoms develop, the disease is known as viral encephalitis. While this infectious disease does not cause fatal symptoms and complications to develop in all cases, it can be deadly in some patients, as it may cause the areas surrounding the brain to become inflamed.

Once exposed to the virus, not all patients will develop severe symptoms or viral encephalitis. Approximately 1% of those individuals exposed to the specific virus that causes the disease develop viral encephalitis. In patients who develop the condition associated with an infection of these viruses, up to 30% may experience more severe symptoms and complications. The condition is more prevalent among children, but can affect people of any age. When a child is infected with the virus, they usually develop an immunity to the virus, which means being exposed to the virus later in life will not cause them to develop Japanese Encephalitis.

What Are The Signs And Symptoms Of Japanese Encephalitis?

The majority of people who are exposed to the virus that causes Japanese Encephalitis will not develop this infectious disease. Their immune system will fight against the infection and appropriately dispose of the virus. In other cases, however, symptoms may develop. Identifying the symptoms early on is very important as the development of viral encephalitis means there is swelling present around the infected person’s brain – this can lead to fatal complications.

Once infected, it may take up to 15 days for symptoms to develop in a patient. Once symptoms start to develop, the patient may start to experience a fever, along with headaches and feeling nauseous. In some cases, the patient may also frequently vomit.

More severe complications that may occur as a result of encephalitis include:

  • The patient may experience a stiff neck.
  • Seizures are not uncommon among individuals who experience a more severe level of complications due to encephalitis.
  • General weakness is also relatively comment, which may be accompanied by movement disorders and complications.
  • Some patients may experience paralysis in some parts of their body.
  • In more severe cases of encephalitis, the patient may also fall into a coma. When a coma occurs, the disease is usually considered fatal, and the failure to acquire prompt care and treatment may result in death.

It should also be noted that when more serious complications associated with Japanese Encephalitis occurs, a patient may experience long-term damage to both their brain and their central nervous system. This can lead to complications being present even after the virus has been cleared up, making prompt diagnosis and treatment of the disease essential.

How Is Japanese Encephalitis Diagnosed?

Since the development of viral encephalitis following the exposure to the virus that causes the disease can lead to life-threatening complications, diagnosis of the disease during the early stages is essential. In many cases, the diagnosis of this infectious disease is difficult, since the early symptoms of the disease can represent particular symptoms often associated with the infection of similar infectious viruses. It is important for physicians and healthcare facilities to obtain additional data from the patient to aid in a more accurate diagnosis of the virus causing their symptoms.

Before a diagnosis of Japanese Encephalitis can be made, a physician will first ask the patient about the symptoms they are experiencing and look at any particular travel destinations they have recently visited. This data will give the physician a better overview of whether or not the patient may be at risk of previously being exposed to the virus that causes this condition and will help them determine if further tests may be needed to identify the presence of encephalitis in the patent.

The most accurate diagnostic testing available for the diagnosis of Japanese encephalitis is to extract cerebrospinal fluid from the patient and test for IgM antibodies that are specific to the virus that causes this infection. It should be noted that it may take up to eight days for these antibodies to become present in the patient’s cerebrospinal fluid following the development of the infection.

Are There Effective Treatments For Japanese Encephalitis?

No cure or particularly effective treatments have been identified for Japanese Encephalitis. There are, however, certain treatment protocols that have been suggested in order to help a patient’s body fight off the virus that causes this viral infection and to reduce the severity of the symptoms during the course of the infection.

In most cases, a patient diagnosed with this disease will be admitted to a hospital. While in hospital, they will be closely monitored in order to detect any signs of complications. Additionally, their fluid and oxygen levels will be kept at an optimal level through the use of different techniques. There are also some medications that can be given to a patient to help reduce fever, inflammation, pain and other symptoms associated with this infectious disease.

Can Japanese Encephalitis Be Prevented?

While not as common as the flu vaccine, a specific vaccine has been developed for the purpose of preventing Japanese encephalitis in people who will be at a high risk of the virus during their travels. The vaccine is available through private healthcare facilities and physicians. It has been designed to help the body build up an immunity against the virus and is effective in approximately 90% of people who receive it.

Paddy fields are a hotspot for the Japanese Encephalitis carrying mosquito

Paddy fields are a hotspot for the Japanese Encephalitis carrying mosquito

How Can You Reduce Your Risk Of Mosquito Bites?

The vaccine used to prevent the Japanese encephalitis viral infection is very effective, but in 10% of cases, it may not work and still put a person at a risk of being infected should they be exposed to the virus. This makes implementing certain steps to prevent being bitten by a mosquito in the first place important. These steps are especially important if a person is planning to travel toward a rural area, as well as when they will go camping.

While outside, a person should ensure they expose most of their skin through proper clothing – long-sleeved shirts, long trousers, shoes with socks and even gloves are all useful. A hat can also help. There is special clothing also available that have been treated with insect repellent chemicals to help ward off mosquitoes and other insects. Any areas of the skin that is still exposed after dressing should be treated with a high-quality insect repellent.

While inside a building or tent, a person should ensure windows and doors are covered with a special gauze that would not allow mosquitoes to enter. Mosquito nets can also be used, but it is important to choose the options that have been treated with insecticides.

Where Is Japanese Encephalitis Most Common?

The virus is more common in some areas of the world – any person planning to travel is advised to learn more about high-risk countries and to take the appropriate precautionary measures should they be planning a visit to one of these countries.

Even though most often associated with Asian countries, Japanese encephalitis has been detected in many other areas as well, including:

  • Japan
  • Nepal
  • Thailand
  • The Republic of Korea
  • Sri Lanka
  • Vietnam

Several areas of China, especially the rural areas, are also considered high-risk regions.


Exposure to the Japanese Encephalitis Virus can cause viral encephalitis, a condition that sometimes leads to fatal complications and even death. No cure has been developed for this viral infection to date, but appropriate treatment protocols can be used to ease symptoms, speed up recovery and potentially avoid dangerous complications from occurring. The first steps, however, involves recognizing the risks and identifying the symptoms early on. Prevention also plays a key role, which can help travellers reduce their risk of infection when visiting a location where the virus is known to be common.