Japanese encephalitis is defined as an acute neuroinvasive infection of the central nervous system caused by the Japanese encephalitis virus, a member of the flavivirus genus [1][2]. The etiologic agent shares phylogenetic proximity with dengue, Zika, yellow fever, and West Nile viruses, replicating within endoplasmic reticulum-derived membranes to trigger profound cellular stress and inflammatory cascades [2]. Clinical manifestation occurs when the virus breaches protective barriers, resulting in direct neuronal injury compounded by uncontrolled host neuroinflammatory responses [2].
Disease overview
Japanese Encephalitis
流行性乙型脑炎
Evidence-backed informationEN 6/7 applicable sections · ZH 6/7 applicable sectionsUpdated Sep 3, 2026
Japanese encephalitis is a mosquito-borne flaviviral infection that functions as a leading cause of virus-induced encephalitis across the Asia-Pacific region [1][2][3]. First documented in Japan during 1871, the illness currently generates an estimated 100,000 clinical cases and approximately 25,000 fatalities worldwide annually [1][3]. Although the vast majority of exposures produce mild or entirely asymptomatic courses, roughly one in two hundred and fifty infections progresses to severe central nervous system involvement [1][3]. The disease predominantly burdens pediatric populations in endemic territories, while adult residents typically acquire natural immunity through prior subclinical exposure [1][3].
Read the full clinical and epidemiological profile7
Following an incubation period spanning four to fourteen days, initial presentations frequently involve nonspecific symptoms such as fever, headache, and gastrointestinal distress, particularly in pediatric patients [1][3]. Approximately one in two hundred and fifty infected individuals develops acute encephalitic syndrome, marked by abrupt high fever, nuchal rigidity, altered mental status, convulsions, and flaccid or spastic paralysis [1][3]. The case fatality ratio among symptomatic patients reaches thirty percent, while survivors commonly experience enduring neuropsychiatric deficits, including memory impairment, speech disturbances, and motor dysfunction [1][3].
The disease maintains endemic circulation across twenty-four nations within the WHO South-East Asia and Western Pacific regions, exposing over three billion residents to potential exposure [1][3]. Transmission is heavily concentrated in rural and peri-urban agricultural landscapes rather than metropolitan centers, where vector breeding sites align with livestock and avian reservoirs [3]. Annual clinical incidence fluctuates significantly across and within endemic territories, occasionally surging beyond ten cases per one hundred thousand individuals during seasonal outbreak periods [1][3]. Pediatric demographics bear the highest disease burden, whereas adult populations typically acquire natural immunity through prior subclinical exposure [1].
Human infection occurs exclusively through the bite of viremic female Culex mosquitoes, with Culex tritaeniorhynchus serving as the primary vector species [1][3]. The virus circulates within enzootic cycles involving domesticated pigs and wild avian species, which function as critical amplifying hosts that maintain high viral loads for vector acquisition [4][3]. Direct human-to-human transmission does not occur, and environmental spread is strictly mediated by arthropod vectors feeding on infected reservoir hosts [3].
JE primarily affects children [1], although individuals of any age may be affected [1], and most adults in endemic countries have natural immunity after childhood infection [1]. People living in areas with documented JEV transmission risk are exposed [1], with 24 countries in WHO South-East Asia and Western Pacific Regions and more than 3 billion people identified as at risk [1]. Arbovirus emergence, including Japanese encephalitis, has been associated with uncontrolled mosquito vector populations [4] and increased air travel [4].
Childhood immunization programs have been associated with a substantial decrease in pediatric JE cases in endemic areas [5], increasing the relative prominence of adult cases [5]. The evidence also links Japanese encephalitis emergence to domesticated-animal amplification [4], uncontrolled mosquito vector populations [4], and increased air travel [4], indicating that vector-borne transmission dynamics and travel-related exposure are relevant public-health considerations [4].
- 1World Health Organization. Japanese encephalitis [Internet]. cited 3 Sept 2026.Available from: https://www.who.int/news-room/fact-sheets/detail/japanese-encephalitis
- 2Sharma 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/
- 3Wikipedia contributors. Japanese encephalitis - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026.Available from: https://en.wikipedia.org/wiki/Japanese_encephalitis
- 4Weaver 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/
- 5Hills 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/
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Official sourcesAuthority, cadence, notes79
Australia NINDSS
Australia
Australian national notifiable diseases surveillance dashboard.
Australia NINDSS — Australian Capital Territory
Australian Capital Territory, Australia
Australian NINDSS monthly state/territory notifications for Australian Capital Territory, kept separate from the Australia national aggregate.
Australia NINDSS — New South Wales
New South Wales, Australia
Australian NINDSS monthly state/territory notifications for New South Wales, kept separate from the Australia national aggregate.
Australia NINDSS — Northern Territory
Northern Territory, Australia
Australian NINDSS monthly state/territory notifications for Northern Territory, kept separate from the Australia national aggregate.
Australia NINDSS — Queensland
Queensland, Australia
Australian NINDSS monthly state/territory notifications for Queensland, kept separate from the Australia national aggregate.
Australia NINDSS — South Australia
South Australia, Australia
Australian NINDSS monthly state/territory notifications for South Australia, kept separate from the Australia national aggregate.
Australia NINDSS — Tasmania
Tasmania, Australia
Australian NINDSS monthly state/territory notifications for Tasmania, kept separate from the Australia national aggregate.
Australia NINDSS — Victoria
Victoria, Australia
Australian NINDSS monthly state/territory notifications for Victoria, kept separate from the Australia national aggregate.
Australia NINDSS — Western Australia
Western Australia, Australia
Australian NINDSS monthly state/territory notifications for Western Australia, kept separate from the Australia national aggregate.
China CDC Weekly
China
Monthly notifiable infectious disease reports published by China CDC.
National Disease Control and Prevention Administration
China
Official China public health bulletin and query portal.
PubMed
China
Biomedical literature discovery feed used as supplementary context.
Public Health Science Data Center
Anhui, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Anhui, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Beijing, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Beijing, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Chongqing, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Chongqing, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Fujian, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Fujian, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Guangdong, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Guangdong, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Gansu, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Gansu, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Guangxi, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Guangxi, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Guizhou, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Guizhou, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Henan, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Henan, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Hubei, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Hubei, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Hebei, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Hebei, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Hainan, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Hainan, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Heilongjiang, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Heilongjiang, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Hunan, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Hunan, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Jilin, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Jilin, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Jiangsu, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Jiangsu, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Jiangxi, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Jiangxi, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Liaoning, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Liaoning, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Inner Mongolia, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Inner Mongolia, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Ningxia, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Ningxia, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Qinghai, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Qinghai, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Sichuan, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Sichuan, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Shandong, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Shandong, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Shanghai, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Shanghai, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Shaanxi, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Shaanxi, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Shanxi, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Shanxi, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Tianjin, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Tianjin, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Xinjiang, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Xinjiang, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Tibet, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Tibet, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Yunnan, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Yunnan, China
Province-level statutory infectious disease report published by the responsible health authority.
Public Health Science Data Center
Zhejiang, China
Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.
Provincial statutory infectious disease monthly report
Zhejiang, China
Province-level statutory infectious disease report published by the responsible health authority.
Hong Kong, China CHP Notifiable Diseases
Hong Kong, China
Hong Kong, China CHP annual notifiable infectious disease CSVs normalized to national monthly totals
JP NIID Weekly
Japan
Japan weekly infectious disease surveillance via NIID/JIHS.
Korea KDCA EID
South Korea
Korea KDCA notifiable infectious disease OpenAPI or portal/KOSIS downloads aggregated to national monthly notification counts.
Singapore CDA Weekly Infectious Diseases Bulletin
Singapore
Singapore national weekly case notifications, combining the official data.gov.sg 2012–2022 CSV history with CDA annual workbooks from 2023 onward; 2023 weekly PDFs are retained as a source fallback.
Taiwan, China CDC NIDSS
Taiwan, China
Taiwan, China monthly notifiable infectious disease open-data CSV feed.