What is Japanese Enchepalitis?

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

In more temperate areas of Asia, JEV transmission is seasonal. In the subtropics and tropics, transmission can occur year-round often during rainy season. For most travelers to Asia, the risk for Japanese Encephalitis is very low but varies based on destination, duration of travel, season and activities

A local newspaper in Bali, reported the percentage of JEV cases in Indonesia in 2016 was as much as 326 cases, most of which occurred in Bali.

In March and April 2018, Public Health Services required JEV vaccination in Bali, Indonesia


JEV is transmitted to humans by infected mosquito bites. JEV is maintained in a cycle involving mosquitoes and vertebrata hosts, mainly pigs and wading birds.


The incubation period is between 5-15 days. Initial symptoms include fever, headaches, diarrhea, nausea and vomiting. Seizures are also common.


Complications include

  • Acute encephalitis
  • Dehydration
  • Cerebral edema
  • Behavior changes
  • Seizures (convulsions)
  • Coma
  • Death


Since there is no antiviral treatment, all treatment methods are for support & stabilization.

Health tips

Please be aware while you’re visiting or living in high-risk areas especially during rainy season. Also, the rural areas in high-risk areas such as rice fields, marshlands or somewhere close to pig farms.

Since Japanese Encephalitis Virus is spreading through mosquitobites, we suggest the following prevention tips:

  • Use insect repellent
  • Wear proper clothing to reduce mosquito bites
  • Minimize outdoor activities during the cooler hours from dusk to dawn
  • Stay in air-conditioned or well-screened rooms
  • Use mosquito net


Medscape Nurse