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Definition

Japanese encephalitis is a mosquito-borne virus 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

These risk factors increase your chance of developing Japanese encephalitis. Tell your doctor if you have any of these risk factors:

  • Living or traveling in certain rural parts of Asia—According to the US Centers for Disease Control and Prevention (CDC), there have been outbreaks of Japanese encephalitis 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. The CDC's Traveler's Health website provides the latest information for international travelers.
  • Being a lab worker who might be exposed to the virus
Symptoms

Symptoms of Japanese encephalitis usually appear 5-15 days after the bite from an infected mosquito. If you experience any of these symptoms, do not assume it is due to Japanese encephalitis. These symptoms may be caused by other conditions. Tell your doctor if you have any of these:

  • 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, and do a physical exam. Tests may include the following:

  • Blood tests to look for antibodies
  • CT scan—a type of x-ray that uses a computer to make pictures of structures inside the body
  • MRI scan—a test that uses magnetic waves to make pictures of structures inside the body
  • Cerebrospinal fluid tests
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.

RESOURCES:

Centers for Disease Control and Prevention
http://www.cdc.gov

Traveler's Health
Centers for Disease Control and Prevention
http://wwwnc.cdc.gov/travel

CANADIAN RESOURCES:

Health Canada
http://www.hc-sc.gc.ca

Public Health Agency of Canada
http://www.phac-aspc.gc.ca

References:

CDC Japanese encephalitis home page. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/japaneseencephalitis/. Accessed November 19, 2009.

Japanese encephalitis. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/japaneseencephalitis/. Accessed April 20, 2007.

Japanese encephalitis. Directors of Health Promotion and Education website. Available at: http: //www.dhpe.org/infect/jpenceph.html. Accessed April 20, 2007.

Japanese encephalitis. EBSCO DynaMed website. Available at: https://dynamed.ebscohost.com/about/about-us. Accessed April 20, 2007.

Japanese encephalitis vaccine. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/vaccines/hcp/vis/vis-statements/je-ixiaro.html. Updated December 7, 2011. Accessed February 24, 2012.

Vaccine is key to preventing outbreaks of Japanese encephalitis. UNICEF website. Available at: http://www.unicef.org/immunization/india_28555.html. Accessed April 20, 2007.

10/1/2013 DynaMed Systematic Literature Surveillance http://www.dynamicmedical.com/what.php : Reimer LJ, Thomsen EK, Tisch DJ, et al. Insecticidal bed nets and filariasis transmission in Papua New Guinea. N Eng J Med. 2013 Aug 22; 369(8):745-53.



Last reviewed December 2013 by David L Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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