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Japanese encephalitis

Japanese encephalitis virus (JEV) is the most important cause of viral encephalitis in Asia, primarily affects children. It is a mosquito-borne flavivirus and belongs to the same genus as dengue, yellow fever, and West Nile viruses.

Most JEV infections are mild (fever and headache) or without apparent symptoms, but approximately 1 in 250 infections results in severe clinical illness. Severe disease is characterized by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, sudden paralysis and ultimately death. The case-fatality rate can be as high as 30% among those with disease symptoms. Of those who survive, 20%–30% suffer permanent intellectual, behavioral or neurological problems such as paralysis, recurrent seizures or the inability to speak.


There is no antiviral treatment for patients with JE. Treatment is supportive to relieve symptoms and stabilize the patient. Therefore, prevention via vaccination is the ultimate treatment.


In Nepal, the vaccine for JEV was introduced in 2009, and at 2015 there were 937 new cases reported. Nepal is an endemic area, at risk for JEV, therefore the importance of vaccination. The JEV vaccination is given once at the age of 12 months, as part of the National childhood immunization program.



1.      Japanese encephalitis – WHO


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