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Japanese Encephalitis: Signs, Symptoms, Treatment, Prognosis, Prevention, Clinical Trials

What is Japanese Encephalitis?

Japanese encephalitis is a type of viral infection of the brain, which spreads through a mosquito bite. It does not spread from one person to another. As of now, there is no cure for Japanese Encephalitis. This disease is commonly found in rural areas all over the South East Asia, the Far East and the Pacific islands. The virus of Japanese encephalitis is found in birds and pigs and gets transmitted to mosquitoes when they bite the infected animals. Hence, this disease is more commonly seen in rural areas where there are rice fields and pig farms.

Japanese encephalitis has no cure. Treatment of Japanese Encephalitis comprises of supportive care of the body and its functions, as it tries to fight this disease. Hospitalization of the patient is required so that the patient can be administered oxygen, fluids and medication for treating symptoms.

What is Japanese Encephalitis?

Signs & Symptoms of Japanese Encephalitis

Many patients suffering from Japanese encephalitis will have no symptoms, or will have symptoms which are mild and short-lived and are usually mistaken for flu. However, as the infection spreads to the brain, severe symptoms can develop in about 6-15 days after the infection which include:

  • High fever.
  • Neck stiffness.
  • Seizures.
  • Confusion.
  • Not being able to speak.
  • Tremor, where there is uncontrollable shaking of the body.
  • Paralysis or muscle weakness.

Death occurs in about one in three patients who develop these serious symptoms from Japanese encephalitis.

The symptoms tend to gradually improve in patients who survive. It can, however, take many months for the patient to make a complete recovery; and those who live often suffer from permanent brain damage, which causes long-term problems, such as muscle twitches, tremors, changes in personality, weakness of muscles, difficulties with learning and paralysis in one limb or more.

Immediate medical attention should be sought if you or anyone you know develop any of these symptoms of Japanese Encephalitis and if you have recently visited, or are still visiting an area where Japanese Encephalitis is present.

Diagnosis of Japanese Encephalitis

  • Many of the diagnostic methods for Japanese Encephalitis do not produce results quickly.
  • Patient’s medical history and physical exam is done where the patient is asked about his/her symptoms and history of mosquito bites.
  • Immunofluorescence tests also help with diagnosis of Japanese encephalitis. In this test, special viral markers are used, which react with the human antibodies, which have been marked with a fluorescent chemical.
  • Tests which involve comparison of the presence and quantity of specific antibodies in the blood or spinal fluid can be done.
  • Blood tests are done to look for any significant changes in the blood cells and other components.
  • The cerebrospinal fluid (CSF) is also tested to detect cells, which indicate infection. In about half of the patients suffering from Japanese encephalitis, there is increase in the levels of CSF protein.
  • MRI scan and CT scan are done to look for changes in certain areas of the brain and to correspond them with the patient’s symptoms.

Treatment for Japanese Encephalitis

There is no cure for Japanese Encephalitis and no specific treatment for it is available. However, supportive care is given to the patient to ease the symptoms and it requires close observation and hospitalization of the patient where symptomatic treatment is done. Appropriate therapeutic interventions need to be started for the right management of intracranial pressure which includes:

  • Patient suffering from Japanese Encephalitis is closely monitored for complications, such as bacterial infections which can include urinary tract infections, pneumonia and decubitus ulcers.
  • Japanese Encephalitis patient is also closely observed for development of co-infection with other tropical diseases, such as malaria and tuberculosis.
  • Supportive care for patients suffering from Japanese encephalitis includes feeding and airway management.
  • Rest should be given to the patient.
  • Lots of fluids, including intravenous fluids are given to keep the Japanese Encephalitis patient hydrated.
  • Medications, such as pain killers are prescribed to patient suffering from Japanese Encephalitis to provide pain relief.
  • Medications are also prescribed to relieve fever if the patient has it.
  • Anticonvulsants are prescribed to prevent and control seizures.
  • Currently, there is no effective antiviral medicine present for Japanese Encephalitis.
  • Invasive monitoring and care is needed for patients who have evidence of increased intracranial pressure.
  • Mannitol (manna sugar, mannite) is used to decrease the intracranial pressure if needed.

Clinical Trials for Japanese Encephalitis

Clinical trials are being carried out, which have shown some amount of benefit from the use of interferon Alfa. Other drugs are Suramin and diethyldithiocarbamate, which have displayed reasonably fair antiviral efficacy against in vitro virus of Japanese encephalitis.

Prognosis of Japanese Encephalitis

  • Death occurs in about 20 to 30% of patients suffering from Japanese encephalitis.
  • Even though there is improvement in some of the symptoms after abatement of the acute illness, about 25% to 50% of the surviving patients continue to suffer from neurologic, psychiatric or cognitive symptoms.
  • Long-term rehabilitation and care is required for patients who have residual neurologic deficits, including movement disorders and seizures.
  • Very rarely, there have been some cases which have had relapse of Japanese encephalitis after many months of recovery.

Prevention of Japanese Encephalitis

  • Getting vaccinated against this dangerous infection before traveling to an area where there is a risk of getting Japanese encephalitis is the best way to prevent it. The risk for catching Japanese encephalitis is more if you want to go camping or hiking or are planning to visit rural areas. The vaccine for Japanese encephalitis can give protection against this disease in more than 9 out of 10 individuals who get it. Vaccination should always be taken when:
  • Visiting high-risk area in rainy season.
  • Visiting high-risk rural areas where there are marshlands, rice fields and pig farms.
  • When working in a laboratory where there can be exposure to the virus.
  • When taking part in activities, which increase the risk of getting mosquito bites and becoming infected, such as camping or cycling.

Precautions for Japanese Encephalitis Vaccine

  • It is important to inform the doctor or other medical professional if you are having high temperature or are pregnant or breastfeeding before being vaccinated.
  • The vaccination can be postponed in case of a fever.
  • Vaccination for Japanese Encephalitis is not recommended in pregnancy and breastfeeding.
  • The vaccine should also not be taken if you’ve had anaphylaxis, which is a severe allergic reaction to any of its ingredients of the vaccine or the vaccine itself in the past.
  • The vaccine for Japanese encephalitis is not recommended for children who are less than two months of age.

Side Effects of Japanese Encephalitis Vaccine

About less than half of individuals who have taken vaccine for Japanese encephalitis experience some short-lived and mild side effects, such as:

Serious side effects of Vaccine for Japanese Encephalitis are rare and include:

  • Facial swelling.
  • Red, itchy, raised rash.
  • Difficulty in breathing.

Precautions should still be taken even if you have been vaccinated, to cut down on the risk of being bitten by an infected mosquito, as the vaccine is not always 100% effective. These precautions comprise of:

  • Wearing long-sleeved tops, long pants and socks.
  • Always sleep in rooms which have close-fitting gauze over the doors and windows.
  • Always use mosquito nets, which have been impregnated with an insecticide when sleeping outdoors.
  • Insect repellent of good quality should be applied to exposed areas of the skin.
  • The room which you are sleeping in should be sprayed with an insecticide in the early evening so that mosquitoes which have got in during the day are killed.
  • The virus of Japanese encephalitis is most active in warm, humid conditions and at dusk, so being outdoors at these times should be avoided.
  • Loose-fitting clothes should be worn as mosquitoes can bite through tight fitting clothes.

Guidelines for Applying Mosquito/Insect Repellant

  • Insect repellent should not be used on wounds, cuts, irritated skin, around the eyes, ears and mouth.
  • It should not be sprayed directly on the face, but should be sprayed on the hands first and then applied to the face.
  • Always help young children in applying the mosquito repellant and never let them apply on their own.
  • Always apply it after applying sunscreen and not before.
  • Thoroughly wash your hands after its usage. The repellent also needs to be washed off the skin using soap and water after coming indoors when it’s no longer needed.
  • Always follow the instructions labeled on the box.


  1. World Health Organization (WHO). (2021). Japanese encephalitis. https://www.who.int/news-room/fact-sheets/detail/japanese-encephalitis
  2. Centers for Disease Control and Prevention (CDC). (2021). Japanese Encephalitis: Signs, Symptoms, and Diagnosis. https://www.cdc.gov/japaneseencephalitis/symptoms/index.html
  3. Travel Health Pro. (2021). Japanese encephalitis. https://travelhealthpro.org.uk/disease/192/japanese-encephalitis
  4. Immunization Action Coalition (IAC). (2020). Japanese Encephalitis (JE) Vaccine. https://www.immunize.org/vis/japanese-encephalitis.pdf
  5. The Lancet. (2014). Japanese encephalitis: new options for active immunisation. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(14)61003-5/fulltext

Also Read:

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 28, 2023

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