Japanese Encephalitis

Japanese encephalitis is a zoonotic, vector-borne flaviviral disease transmitted by mosquitoes, with Japanese encephalitis virus (JEV) as the causative agent ^[1][2]. The disease is characterized by neuroinvasive infection and is described as the leading global cause of virus-induced encephalitis, with particularly strong burden in the Asia-Pacific region ^[1]. In the available sources, it is also framed as an infection with potential for wider geographic spread beyond currently endemic areas ^[1][2].

The clinical spectrum ranges from mild fever to severe encephalitis and death ^[1]. Available sources describe Japanese encephalitis as having severe neurological manifestations and note that most infections are asymptomatic or only mildly symptomatic ^[2]. One source reports that about one-third of infections are fatal and that half of survivors develop permanent neurological sequelae ^[1], while another gives a case-fatality range of 20–30% and serious sequelae in 30–50% of survivors ^[2]. Source-backed detail on timing, specific neurologic signs, and clinical course in individual patients is not yet available.

Japanese encephalitis is reported as predominant in the Asia-Pacific region, with endemic transmission in Asia and the potential for global spread ^[1][2]. One source estimates that the population at risk is approximately 3 billion people ^[2]. The disease burden is described as concentrated in children in endemic areas, whereas adults become more prominent when transmission extends into new areas or when childhood immunization reduces pediatric cases ^[3][2]. Recent expansion of transmission has been documented, including a markedly expanded area in Australia during 2021–2022 ^[3].

JEV is spread by the bite of carrier Culex mosquitoes ^[1]. The sources also describe Japanese encephalitis as an arthropod-borne infection whose emergence can be linked to enzootic wildlife cycles and secondary amplification in domesticated animals ^[4]. Detailed source-backed information on persistence, seasonality, or specific ecological amplifying hosts is not yet available in the provided material.

The available sources identify children as the main burden group in endemic areas, while adults may be more affected where transmission is newly established or where childhood immunization has reduced pediatric disease ^[3][2]. Adult travelers to JE risk areas are also described as a group with increased exposure because they are usually non-immune ^[3]. Source-backed detail on other specific high-risk occupational, behavioral, or clinical groups is not yet available.

General prevention in the available sources focuses on avoiding mosquito bites, including use of repellents, long-sleeved clothing, coils, and vaporizers ^[2]. The metadata also notes vaccine prevention, including live attenuated JE vaccines, recombinant chimeric JE vaccines, and cell culture-derived inactivated JE vaccines ^[2]. As animal reservoirs of JEV cannot be eradicated, source material indicates that vaccination and exposure reduction are key control measures ^[2].

In surveillance, Japanese encephalitis should be read as a vector-borne neuroinvasive disease whose burden may shift with geographic expansion, childhood immunization coverage, and travel-related exposure ^[3][2]. Adult cases may become more visible where transmission newly appears or where pediatric disease has fallen after control programs ^[3]. Monitoring should therefore pay attention to both endemic pediatric burden and emerging adult or traveler cases in new risk areas ^[3][5].

1. 1 Sharma KB et al. Pathobiology of Japanese encephalitis virus infection. Mol Aspects Med. 2021 Oct. PMID: 34274157. doi: 10.1016/j.mam.2021.100994. PubMed: https://pubmed.ncbi.nlm.nih.gov/34274157/
2. 2 Japanese Encephalitis. VacciTUTOR. 2021. doi: 10.33442/vt202149. DOI: https://doi.org/10.33442/vt202149
3. 3 Hills SL et al. Japanese Encephalitis among Adults: A Review. Am J Trop Med Hyg. 2023 May 3. PMID: 37037440. doi: 10.4269/ajtmh.23-0036. PubMed: https://pubmed.ncbi.nlm.nih.gov/37037440/
4. 4 Weaver SC et al. Zika, Chikungunya, and Other Emerging Vector-Borne Viral Diseases. Annu Rev Med. 2018 Jan 29. PMID: 28846489. doi: 10.1146/annurev-med-050715-105122. PubMed: https://pubmed.ncbi.nlm.nih.gov/28846489/
5. 5 Japanese encephalitis. Practice Nursing. 2002. doi: 10.12968/pnur.2002.13.11.13011. DOI: https://doi.org/10.12968/pnur.2002.13.11.13011
6. 6 Japanese Encephalitis. Jurnal Kedokteran dan Kesehatan Indonesia. 2019. doi: 10.20885/jkki.vol10.iss1.art2. DOI: https://doi.org/10.20885/jkki.vol10.iss1.art2

ICD-10

A83.0

ICD-11

1C83.0

Total cases

18K

Total deaths

723

Peak month

2010-08

Coverage

6 reporting countries · 2000-01-01 → 2025-10-01