Key points
- Japanese encephalitis virus is spread through the bite of an infected mosquito.
- Most people with Japanese encephalitis do not have symptoms or have only mild symptoms.
- Some people develop inflammation of the brain, with symptoms including headache, fever, disorientation, seizures, weakness, and coma.
- Vaccination is recommended for some travelers.
Overview
Japanese encephalitis virus is transmitted to humans through the bites of infected Culex species mosquitoes, particularly Culex tritaeniorhynchus. Japanese encephalitis virus is the leading cause of vaccine-preventable encephalitis in Asia and the western Pacific. For most travelers to Asia, the risk for Japanese encephalitis is very low but varies based on destination, length of travel, season, and activities.
Most people infected with Japanese encephalitis do not have symptoms or have only mild symptoms. However, a small percentage of infected people develop inflammation of the brain (encephalitis), with symptoms including headache, fever, disorientation, seizures, weakness, and coma. Among patients who develop encephalitis, about 1 in 4 (20–30%) die.
The best way to prevent Japanese encephalitis is to protect yourself from mosquito bites. Vaccination is recommended for some travelers.