Know Japanese Encephalitis: Symptoms, Prevention

Know Japanese Encephalitis: Symptoms, Prevention


Japanese Encephalitis is a mosquito-borne viral encephalitis caused by a flavivirus. It is one of the most important endemic encephalitis in the world especially in Eastern and Southern Asia. Japanese Encephalitis is a flavivirus related to dengue, yellow fever, and West Nile viruses. In the WHO South-East Asia and Western Pacific regions 24 countries have endemic Japanese Encephalitis Virus transmission, exposing more than 3 billion people to the risk of infection.  Globally, 75% of cases occur in children and adolescents, making Japanese Encephalitis the leading cause of viral childhood encephalitis in Asia. The fatality rate of Japanese Encephalitis among severe cases can be as high as 30% and permanent neurologic or psychiatric sequelae can occur in further 30-50% of cases. Japanese encephalitis virus accidentally infects human and are a dead-end host because of low level and transient viremia. The main zoonotic cycle of Japanese Encephalitis virus revolves around mosquitoes, pigs and water birds.


JEV is an arthropod-borne virus (arbovirus) that is transmitted in an enzootic cycle among mosquito vectors and vertebrate hosts, particularly pigs and birds;. Japanese Encephalitis virus is transmitted to humans through the bite of infected Culex mosquitoes.


The manifestations of the disease depend on which part of the nervous system is affected and include early symptoms, such as nonspecific febrile illness, viz. diarrhea and rigor, followed by symptoms such as reduced levels of consciousness, seizures, headache, photophobia, and vomiting in the next stage. Symptomatic Japanese Encephalitis virus can cause a spectrum of symptoms.

  • The prodromal phase of the disease begins with flu-like non-specific symptoms like fever vomiting, headache, the malaise that may last for several days.
  • Undifferentiated febrile illness
  • The mild febrile illness is followed by the acute encephalitis phase, in which a variety of neurological symptoms manifest themselves like mental status change, focal neurologic deficit, and movement disorders.
  • Japanese Encephalitis patients may show a parkinsonian syndrome and they also experience Polio-like acute flaccid paralysis.
  • Convulsions and abnormal behavior are common in children, whereas febrile illness and meningism occur frequently in adults.


Prevention and control

  • A safe and effective way to prevent transmission of Japanese Encephalitis is the vaccine. WHO recommends having strong JE prevention and control activities, including JE immunization in all regions where the disease is a recognized public health priority, along with strengthening surveillance and reporting mechanisms. Even if the number of JE-confirmed cases is low, vaccination should be considered where there is a suitable environment for JE virus transmission.
  • Travelers to the Japanese Encephalitis-endemic areas should take precautions to avoid mosquito bites.
  • Remaining strategies that repel mosquitoes away from residence should be applied like, fogging.
  • Personal preventive measures include the use of mosquito repellents, long-sleeved clothes, coils, and vaporizers.








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