Japanese encephalitis
Japanese encephalitis is a mosquito-borne viral infection found in parts of Asia and the western Pacific. Most infections cause no symptoms. A small proportion cause inflammation of the brain, which can be fatal or leave lasting neurological problems. For most travelers the risk is very low, but rural exposure, longer stays and outdoor activities can increase it.
Prevention: Mixed
Symptoms
- Often no symptoms
- Fever, headache and vomiting when illness develops
- Severe illness may cause confusion, weakness or seizures
Transmission
- Bites from infected mosquitoes, mainly Culex species
- The virus normally circulates between mosquitoes, pigs and birds; people are incidental hosts
Prevention
Use mosquito repellent, covering clothing and screened sleeping areas, particularly with evening or nighttime exposure. Vaccination may be appropriate depending on the itinerary, season, length of stay and activities. A travel-health professional can assess these factors and local recommendations.
Diagnosis and care
Fever with confusion, seizures or new weakness needs emergency care. There is no specific antiviral treatment; hospital care supports breathing and other body functions and manages complications.
Source
- Japanese Encephalitis
Based on CDC information
Source language: English
Source reviewed: February 20, 2026
Source accessed: May 17, 2026
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