Japanese Encephalitis: A Preventable but Deadly Disease

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Japanese B Encephalitis: A Preventable but Serious Disease


Japanese B encephalitis (JBE) is a mosquito-borne viral infection of the brain that is found in several Asian countries. It is the leading cause of viral encephalitis (inflammation of the brain) in Asia, and is a major public health concern in many countries in the region.


JBE is caused by the Japanese B encephalitis virus (JEV), which is transmitted to humans through the bite of an infected mosquito. The virus is most commonly found in rural areas where pigs and rice paddies are common, as these environments provide ideal breeding grounds for the mosquitoes that transmit the virus.


The incubation period for JBE is typically 5 to 15 days. The symptoms of JBE can vary, but may include:

  • Fever
  • Headache
  • Nausea and vomiting
  • Stiff neck
  • Sensitivity to light
  • Confusion
  • Seizures
  • Coma


JBE can be diagnosed based on the patient’s symptoms, as well as laboratory tests to detect the virus or antibodies against the virus in the blood or cerebrospinal fluid.


There is no specific treatment for JBE. Treatment is supportive and may include:

  • Restricting the patient’s activity
  • Providing fluids and electrolytes
  • Medications to reduce fever and inflammation
  • Anticonvulsants to control seizures
  • Mechanical ventilation if necessary


The most effective way to prevent JBE is through vaccination. The JBE vaccine is safe and effective, and is recommended for people who live in or travel to areas where the virus is found.

Other preventive measures include:

  • Avoiding areas where mosquitoes are prevalent, especially during the evening and early morning hours when mosquitoes are most active
  • Wearing long sleeves and pants when outdoors
  • Using mosquito repellent containing DEET, picaridin, or IR3535
  • Sleeping under mosquito nets


JBE can lead to a variety of complications, including:

  • Encephalitis (inflammation of the brain)
  • Meningitis (inflammation of the membranes that surround the brain and spinal cord)
  • Seizures
  • Paralysis
  • Cognitive impairment
  • Death


The outlook for people with JBE varies depending on the severity of the infection and the promptness of treatment. Approximately 20 to 30% of people with JBE die, and another 30 to 50% experience permanent neurological damage.


JBE is a serious but preventable disease. Vaccination is the most effective way to prevent JBE, and other preventive measures can also help to reduce the risk of infection. If you are traveling to an area where JBE is found, be sure to consult with your healthcare provider about the vaccine and other preventive measures.

Additional Information

  • The JBE vaccine is available in two forms: a live attenuated vaccine and an inactivated vaccine. The live attenuated vaccine is more effective than the inactivated vaccine, but it can cause mild side effects, such as fever and headache. The inactivated vaccine is less effective than the live attenuated vaccine, but it is also less likely to cause side effects.
  • JBE is a notifiable disease in many countries, which means that healthcare providers are required to report suspected cases to the local health authorities. This helps to track the spread of the virus and to ensure that appropriate control measures are in place.
  • Research is ongoing to develop new and more effective JBE vaccines and treatments.

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