Japanese encephalitis



What is Japanese encephalitis?

Japanese encephalitis (JE) is a condition caused by Japanese encephalitis virus, the leading cause of vaccine-preventable encephalitis in Asia and the western Pacific. For most travelers to Asia, the risk for JE is very low but varies based on destination, duration of travel, season, and activities.

JE virus is maintained in a cycle involving mosquitoes and vertebrate hosts, mainly pigs and wading birds. Humans can be infected when bitten by an infected mosquito. Most human infections are asymptomatic or result in only mild symptoms.

However, a small percentage of infected persons develop inflammation of the brain (encephalitis), with symptoms including sudden onset of headache, high fever, disorientation, coma, tremors and convulsions. About 1 in 4 cases are fatal. There is no specific treatment for JE. Patient management focuses on supportive care and management of complications. Steps to prevent JE include using personal protective measures to prevent mosquito bites and vaccination. 

How common is Japanese encephalitis?

Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia, with up to 70,000 cases reported annually. Please discuss with your doctor for further information.


What are the symptoms of Japanese encephalitis?

The common symptoms of Japanese encephalitis are

  • Fever, headache, and vomiting.
  • Mental status changes, neurologic symptoms, weakness, and movement disorders might develop over the next few days.
  • Seizures are common, especially among children.

When should I see my doctor?

If you have any signs or symptoms listed above or have any questions, please consulting with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.


What causes Japanese encephalitis?

Japanese encephalitis (JE) virus, a flavivirus, is closely related to West Nile and St. Louis encephalitis viruses. It is transmitted to humans through the bite of infected Culex species mosquitoes, particularly Culex tritaeniorhynchus.

The virus is maintained in a cycle between mosquitoes and vertebrate hosts, primarily pigs and wading birds. Humans are incidental or dead-end hosts, because they usually do not develop high enough concentrations of JE virus in their bloodstreams to infect feeding mosquitoes.

JE virus transmission occurs primarily in rural agricultural areas, often associated with rice production and flooding irrigation. In some areas of Asia, these conditions can occur near urban centers.

In temperate areas of Asia, JE virus transmission is seasonal. Human disease usually peaks in the summer and fall. In the subtropics and tropics, transmission can occur year-round, often with a peak during the rainy season.

Risk factors

What increases my risk for Japanese encephalitis?

You may have higher risks for this condition if you are experiencing these following conditions:

  • Residents of rural areas in endemic locations
  • Active duty military deployed to endemic areas
  • Expatriates who visit rural areas

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is Japanese encephalitis diagnosed?

If your doctor suspects you may experience Japanese encephalitis, he or she may perform a physical examination. And some tests may be then recommended by your doctor.

Laboratory diagnosis of JE is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect virus-specific IgM antibodies. JE virus IgM antibodies are usually detectable 3 to 8 days after onset of illness and persist for 30 to 90 days, but longer persistence has been documented. Therefore, positive IgM antibodies occasionally may reflect a past infection or vaccination. Serum collected within 10 days of illness onset may not have detectable IgM, and the test should be repeated on a convalescent sample. For patients with JE virus IgM antibodies, confirmatory neutralizing antibody testing should be performed. In fatal cases, nucleic acid amplification, histopathology with immunohistochemistry, and virus culture of autopsy tissues can also be useful.

How is Japanese encephalitis treated?

Unfortunately, no specific treatments have been found to benefit patients with JE, but hospitalization for supportive care and close observation is generally required.

Treatment is symptomatic. Rest, fluids, and use of pain relievers and medication to reduce fever may relieve some symptoms. According to some surveys, among patients who develop encephalitis, 20% – 30% die.

Although some symptoms improve after the acute illness, 30%-50% of survivors continue to have neurologic, cognitive, or psychiatric symptoms.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage Japanese encephalitis?

The following lifestyles and home remedies might help you cope with Japanese encephalitis:

Avoid Mosquito Bites

  • You should use Insect Repellent

When you go outdoors, use an EPA-registered insect repellent such as those containing DEET, IR3535, picaridin or oil of lemon eucalyptus. Even a short time outdoors can be long enough to get a mosquito bite.

  • Wear Proper Clothing to Reduce Mosquito Bites

When weather permits, wear long-sleeves, long pants and socks when outdoors.

  • Reduce Exposure to Mosquitoes During Peak Biting Hours

The mosquitoes that transmit JE virus feed mainly outside during the cooler hours from dusk to dawn. Travelers to high risk areas should consider minimizing outdoor activities at these times if possible.

Obtain Vaccine if Recommended

  • JE vaccine is recommended for travelers who plan to spend 1 month or more in endemic areas during the JE virus transmission season. Vaccine should also be considered for the following:
  • Short-term (less than 1 month) travelers to endemic areas during the transmission season, if they plan to travel outside an urban area and their activities will increase the risk of JE virus exposure.
  • Travelers to an area with an ongoing JE outbreak.
  • Travelers to endemic areas who are uncertain of specific destinations, activities, or duration of travel.
  • JE vaccine is not recommended for short-term travelers whose visits will be restricted to urban areas or times outside a well-defined JE virus transmission season.

If you have any questions, please consult with your doctor to better understand the best solution for you

Hello Health Group does not provide medical advice, diagnosis or treatment.


Review Date: August 21, 2017 | Last Modified: August 22, 2017

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