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Japanese Encephalitis virus (a mosquito-borne viral infection) is the leading cause of Encephalitis in Asia and the western Pacific. For most travelers to Asia, the risk for JE is low but varies based on the destination, length of travel, season, and activities. Most people infected with JE do not have symptoms or have only mild symptoms. However, a small percentage of infected people develop inflammation of the brain (Encephalitis),

Inactivated Vero Cell culture-derived Japanese encephalitis (JE) vaccine (manufactured as IXIARO) is the only JE vaccine licensed and available in the United States. This vaccine was approved in March 2009 for use in people aged 17 years and older and in May 2013 for use in children two months through 16 years of age. Other JE vaccines are manufactured and used in other countries but not licensed for use in the United States.

The vaccine is recommended for people who:


  • Plan to live in a country where JE occurs,

  • Plan to visit a country where JE occurs for extended periods (e.g., one month or more), or

  • Frequently travel to countries where JE occurs.


It should also be considered for travelers spending less than one month in a country where JE occurs if they:


· Will visit rural areas and have an increased risk for mosquito bites,

· Are not sure of their travel plans.


The vaccine is given as a 2-dose series. A booster dose is recommended after a year for people who remain at risk.

A person with Japanese Encephalitis will probably have no symptoms, but if there are symptoms, they will appear 5 to 15 days after being infected.


A person with mild Japanese Encephalitis might only develop a fever and a headache, but more severe symptoms can develop quickly.


Possible symptoms include:

  • a headache

  • high fever

  • tremors

  • nausea

  • vomiting

  • stiff neck

  • spastic paralysis


A person might also experience changes to brain function, including:

  • stupor

  • disorientation

  • coma

  • convulsions in children

  • The testicles can also swell.


The brain symptoms of Japanese Encephalitis can cause lifelong complications, such as deafness, uncontrollable emotions, and weakness on one side of the body. The chance of surviving the disease varies, but children face the highest risk of fatal consequences.

To prevent Japanese Encephalitis, avoid mosquito bites in rural areas, specifically close to irrigated rice fields and pig farms. Many mosquitoes are most active at dusk and dawn. People can use insect repellents when outdoors and wear long sleeves and trousers at these times, or consider staying indoors during these hours and getting vaccinated.

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