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Japanese Encephalitis

  • Definition

    Japanese encephalitis is a mosquito-borne infection that leads to swelling of the brain. It can affect the central nervous system and cause severe complications, even death.
  • Causes

    Japanese encephalitis can occur if you are bitten by a mosquito infected with the virus.
  • Risk Factors

    Factors that may increase your chance of Japanese encephalitis include:
    • Living or traveling in certain rural parts of Asia—Outbreaks have occurred in China, Korea, Japan, Taiwan, and Thailand. These countries have controlled the disease through vaccinations . Other countries that still have periodic epidemics include Vietnam, Cambodia, Myanmar, India, Nepal, and Malaysia.
    • Employment as a lab worker, which may result in exposure to the virus.
  • Symptoms

    Symptoms of Japanese encephalitis usually appear 5-15 days after the bite from an infected mosquito.
    Japanese encephalitis may cause:
    • Agitation
    • Brain damage
    • Chills
    • Coma
    • Confusion
    • Convulsions (especially in infants)
    • Fever
    • Headache
    • Nausea
    • Neck stiffness
    • Paralysis
    • Tiredness
    • Tremors
    • Vomiting
  • Diagnosis

    Your doctor will ask about your symptoms and medical history. A physical exam will be done.
    Tests may include the following:
    • Blood tests to look for antibodies
    • Cerebrospinal fluid tests to evaluate the fluid that surrounds the brain and spinal cord
    Imaging tests to assess the brain include:
  • Treatment

    Since there is no specific treatment for Japanese encephalitis. Care is focused on treating specific symptoms and complications.
  • Prevention

    There is a Japanese encephalitis vaccine . It is recommended for people who live or travel in certain parts of Asia and for lab workers who are at risk of exposure to the virus.
    Also, take the following measures to protect yourself from mosquito bites:
    • Remain in well-screened areas.
    • Wear clothes that cover most of your body.
    • Use insect repellents that contain up to 30% NN-diethyl-meta-toluamide (DEET) on skin and clothing.
    • Use proper mosquito netting at night. Look for netting treated with insecticide.

    Infectious Disease Society of America

    Traveler's HealthCenters for Disease Control and Prevention


    Health Canada

    Public Health Agency of Canada


    Japanese encephalitis. Centers for Disease Control and Prevention website. Available at: Accessed November 12, 2012. Accessed November 13, 2014.

    Japanese encephalitis. EBSCO DynaMed website. Available at: Updated February 12, 2014. Accessed November 13, 2014.

    Japanese encephalitis VIS. Centers for Disease Control and Prevention website. Available at: Updated January 24, 2014. Accessed November 13, 2014.

    Vaccine is key to preventing outbreaks of Japanese encephalitis. UNICEF website. Available at: Accessed November 13, 2014.

    10/1/2013 DynaMed Systematic Literature Surveillance Reimer LJ, Thomsen EK, Tisch DJ, et al. Insecticidal bed nets and filariasis transmission in Papua New Guinea. N Eng J Med. 2013;369(8):745-753.

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