Japanese encephalitis
Mosquito-borne brain infection endemic in Asia and the Western Pacific.
The World Health Organization states that JEV is a flavivirus related to dengue, yellow fever and West Nile viruses.[1] The Japanese encephalitis virus (JEV) is the causative agent of a brain infection known as Japanese encephalitis.[2] Regions where this disease is found include East Asia, Southeast Asia, and the Western Pacific area.[3]
Last updated 2026-10-07 from the source article.
Quick Facts
- Field
- Infectious disease
- Symptoms
- Headache
- fever
- vomiting
- confusion
- seizures
- Onset
- 5 to 15 days after infection
- Causes
- Japanese encephalitis virus (spread by mosquitoes)
- Diagnosis
- Blood or cerebrospinal fluid testing
- Prevention
- Japanese encephalitis vaccine, avoiding mosquito bites
- Treatment
- Supportive care
- Prognosis
- Permanent neurological problems occur in up to half of survivors
Facts from the source article.
Key facts and history
The case-fatality rate among those with encephalitis can be as high as 30%.[1] Permanent neurologic, cognitive and behavioural sequelae occur in 30–50% of those with encephalitis.[1] A clinical case of Japanese encephalitis was first recorded in Japan in the year 1871.[1][4] Mosquitoes, particularly those belonging to the Culex genus, are the typical vectors for JEV transmission.[5]
The virus finds a reservoir in both pigs and wild bird populations.[5] Administering the Japanese encephalitis vaccine is the primary method of prevention, and it is considered safe and effective.[6] No specific treatment exists for those who contract the infection; medical care is focused on supportive measures.[6][7]
What the research sources say
The World Health Organization notes that symptomatic Japanese encephalitis is rare.[1] The CDC reports that the case-fatality rate for patients with encephalitis is approximately 20–30%.[8] The CDC adds that among survivors, 30–50% have serious neurologic, cognitive, or psychiatric sequelae.[8] The World Health Organization describes JEV as the main cause of viral encephalitis in many countries of Asia.[1]
According to the CDC, the most commonly identified clinical form of infection with the Japanese encephalitis virus is acute encephalitis.[8] The CDC identifies the Japanese encephalitis virus as the leading cause of encephalitis in Asia that can be prevented through vaccination.[8]
References
- "Japanese encephalitis", World Health Organization, December 2015. facts only, no text reused. who.int
- Wikipedia, "Japanese encephalitis" (CC BY-SA 4.0), which cites: "Japanese Encephalitis", CDC, August 2015; "Japanese Encephalitis", CDC, August 2015; "Symptoms and Treatment", CDC, August 2015; "Symptoms and Treatment", CDC, August 2015 (original not read by us) en.wikipedia.org
- Wikipedia, "Japanese encephalitis" (CC BY-SA 4.0), which cites: "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis - Causes", 6 February 2019 (we also read that source) en.wikipedia.org
- Wikipedia, "Japanese encephalitis" (CC BY-SA 4.0), which cites: Erlanger, "Past, Present, and Future of Japanese Encephalitis", Emerging Infectious Diseases, January 2009, p. 1–7; Fernando, "Japanese encephalitis virus spreads to new areas", RACGP, 10 January 2025 (original not read by us) en.wikipedia.org
- Wikipedia, "Japanese encephalitis" (CC BY-SA 4.0), which cites: "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015 (we also read that source) en.wikipedia.org
- Wikipedia, "Japanese encephalitis" (CC BY-SA 4.0), which cites: "Japanese encephalitis", World Health Organization, December 2015; "Japanese encephalitis", World Health Organization, December 2015; "Symptoms and Treatment", CDC, August 2015; "Symptoms and Treatment", CDC, August 2015; "Japanese encephalitis", World Health Organization, December 2015 (we also read that source) en.wikipedia.org
- Wikipedia, "Japanese encephalitis" (CC BY-SA 4.0), which cites: "Japanese encephalitis", Journal of Neurology, Neurosurgery, and Psychiatry, 2000, p. 405–15 (original not read by us) en.wikipedia.org
- "Japanese Encephalitis - Chapter 4 - 2024 Yellow Book Travelers' Health CDC", wwwnc.cdc.gov, 2024. facts only, no text reused. wwwnc.cdc.gov
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Japanese encephalitis (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
More in Viral Infections
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced