This neurotropic flavivirus belongs to the Japanese encephalitis antigenic complex within the family Flaviviridae [2]. It was first isolated in Uganda in 1937 and is maintained in nature through a mosquito-bird-mosquito transmission cycle [2][5]. Birds act as reservoir hosts, while Culex species mosquitoes function as the principal vectors [2][4].
Disease overview
West Nile virus
西尼罗病毒
Evidence-backed informationEN 5/7 applicable sections · ZH 5/7 applicable sectionsUpdated Sep 3, 2026
West Nile virus is a flavivirus responsible for significant morbidity and mortality across birds, horses, and humans globally [1][2]. Following its expansion into North America in the late 1990s, it became endemic throughout the contiguous United States [3]. While most infections are asymptomatic, the virus causes febrile illness and occasionally severe neurological conditions [4]. Management currently depends on supportive care and vector control due to the lack of a licensed human vaccine [1][5].
Read the full clinical and epidemiological profile6
Human clinical presentations vary widely, ranging from asymptomatic infection to mild febrile illness [1][4]. Less than one percent of infections progress to neuroinvasive diseases such as meningitis, encephalitis, or acute flaccid paralysis [3][4]. Neuroinvasive disease carries an overall fatality rate of approximately ten percent, which increases significantly in older adults and immunocompromised patients [4]. Survivors frequently experience long-term sequelae including fatigue, weakness, and cognitive deficits [3][4].
Epidemics have been localized to Europe, Africa, the Middle East, parts of Asia, and North America [1][2]. In the United States, annual reports from 2014 to 2023 indicate a mean of 1300 neuroinvasive disease cases and 130 deaths [4]. Incidence peaks during summer months, particularly in the Midwest region [3]. Large outbreaks have also been documented in Europe, Tunisia, Israel, and the US since 2018 [4].
Human infection occurs primarily through bites from infected mosquitoes that have fed on viremic birds [2][4]. The virus enters the mosquito's salivary glands and is injected during subsequent blood meals [2]. Rare transmission events have been recorded via blood transfusion, organ transplantation, and transplacental routes [2][4]. Climate changes affecting mosquito activity may facilitate year-round transmission in certain regions [5].
Control strategies employ integrated pest management focused on surveillance and eliminating mosquito breeding sites [3]. Aggressive adult mosquito control is emphasized during outbreaks to reduce the abundance of infected biting mosquitoes [3]. Innovative approaches include the use of genetically modified mosquitoes and novel insecticides [5].
- 1Rossi SL et al. West Nile virus. Clin Lab Med. 2010 Mar. PMID: 20513541. doi: 10.1016/j.cll.2009.10.006.PubMed: https://pubmed.ncbi.nlm.nih.gov/20513541/
- 2World Health Organization. West Nile virus [Internet]. cited 4 Sept 2026.Available from: https://www.who.int/news-room/fact-sheets/detail/west-nile-virus
- 3Petersen LR et al. West Nile virus: review of the literature. JAMA. 2013 Jul 17. PMID: 23860989. doi: 10.1001/jama.2013.8042.PubMed: https://pubmed.ncbi.nlm.nih.gov/23860989/
- 4Gould CV et al. West Nile Virus: A Review. JAMA. 2025 Aug 19. PMID: 40622703. doi: 10.1001/jama.2025.8737.PubMed: https://pubmed.ncbi.nlm.nih.gov/40622703/
- 5Singh P et al. West Nile Virus in a changing climate: epidemiology, pathology, advances in diagnosis and treatment, vaccine designing and control strategies, emerging public health challenges - a comprehensive review. Emerg Microbes Infect. 2025 Dec. PMID: 39614679. doi: 10.1080/22221751.2024.2437244.PubMed: https://pubmed.ncbi.nlm.nih.gov/39614679/
Coverage
Reporting countries and regions
AustraliaAU
AustriaAT
BelgiumBE
BulgariaBG
CanadaCA
CroatiaHR
CyprusCY
CzechiaCZ
DenmarkDK
EstoniaEE
FinlandFI
FranceFR
GermanyDE
GreeceGR
Hong Kong, ChinaHK
HungaryHU
IcelandIS
IrelandIE
ItalyIT
JapanJP
LatviaLV
LiechtensteinLI
LithuaniaLT
LuxembourgLU
MaltaMT
NetherlandsNL
NorwayNO
PolandPL
PortugalPT
RomaniaRO
SlovakiaSK
SloveniaSI
South KoreaKR
SpainES
SwedenSE
SwitzerlandCH
United KingdomGB
United StatesUS
Trends by reporting country
Monthly patterns over time
Research Radar
Recent related research
Isolation and molecular characterization of West Nile Virus with evidence of vertical transmission in the Coastal region, Kenya.
Microbiology spectrum
Strengthening mosquito control to manage emerging mosquito-borne diseases
Eurosurveillance
Investigating antibody cross-reactivity and transmission dynamics of alphaviruses and flaviviruses using a multiplex serological assay
Nature Communications
A human cerebral organoid model of West Nile virus encephalitis shows innate immunocompetency
Nature Communications
First detection of West Nile virus in Belgium through wild bird surveillance, Belgium, 2025
Eurosurveillance
Showing 5 of 16 related publications.
Literature links are provided for discovery and do not alter or validate the surveillance series above.
Data access
Page dataset index with source links and update metadata.
Official sourcesAuthority, cadence, notes52
Austria AGES Radar for Infectious Diseases
Austria
AGES Radar monthly national source. Internal ingestion retains native categories; public release is disabled pending licence review.
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.
ECDC Surveillance Atlas — Belgium Annual Baseline
Belgium
Belgium annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Bulgaria Annual Baseline
Bulgaria
Bulgaria annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Canada PHAC CNDSS Annual
Canada
Canada is the national jurisdiction; subdivision feeds are registered separately.
Public Health Ontario IDTO Monthly
Ontario, Canada
Ontario-level current-year preliminary monthly case counts from Public Health Ontario's IDTO report.
Switzerland FOPH IDD
Switzerland
Switzerland FOPH/BAG IDD mandatory reporting API normalized to national case rows. Monthly series may use the dashboard CHFL aggregate where CH-only monthly series are not exposed.
ECDC Surveillance Atlas — Cyprus Annual Baseline
Cyprus
Cyprus annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Czechia Annual Baseline
Czechia
Czechia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Germany RKI SurvStat 2.0
Germany
RKI SurvStat national weekly notification export; raw ZIP exports are retained and recent weeks are overwritten for revisions.
ECDC Surveillance Atlas — Denmark Annual Baseline
Denmark
Denmark annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Estonia Annual Baseline
Estonia
Estonia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Spain Annual Baseline
Spain
Spain annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Finland THL Infectious Diseases Register
Finland
Finland THL Infectious Diseases Register national monthly case counts. The current month is ingested as provisional and the latest three months are refreshed for source revisions.
ECDC Surveillance Atlas — France Annual Baseline
France
France annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — United Kingdom Annual Baseline
United Kingdom
United Kingdom annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Greece Annual Baseline
Greece
Greece annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Hong Kong, China CHP Notifiable Diseases
Hong Kong, China
Hong Kong, China CHP annual notifiable infectious disease CSVs normalized to national monthly totals
ECDC Surveillance Atlas — Croatia Annual Baseline
Croatia
Croatia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Hungary Annual Baseline
Hungary
Hungary annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Ireland HPSC Notifiable Diseases Hub
Ireland
Ireland HPSC national weekly notifiable-disease totals from the official ArcGIS FeatureServer. Internal ingestion is enabled; public release remains disabled pending written redistribution permission.
Iceland Directorate of Health Annual Dashboard
Iceland
National annual case notifications by disease. Published values can be revised retrospectively and remain annual period totals.
Iceland Directorate of Health STI Dashboard
Iceland
Monthly STI diagnosis facts from laboratory and registry surveillance; the official dashboard is published on a quarterly schedule.
Iceland Directorate of Health Respiratory Dashboard
Iceland
ISO-week respiratory diagnosis counts. Hospitalizations, samples, and vaccination indicators are separate measures and are not counted as diagnoses.
Iceland Directorate of Health Historical Registry
Iceland
Historical official registry tables for 1997–2021, with annual totals and disease-specific monthly notification facts retained at source grain.
Iceland Directorate of Health Legacy ICD Monthly
Iceland
Historical Saga EHR ICD encounter counts for 1997–2020. This clinical measure is non-comparable with registry notifications and is kept separate.
ECDC Surveillance Atlas — Italy Annual Baseline
Italy
Italy annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
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.
ECDC Surveillance Atlas — Liechtenstein Annual Baseline
Liechtenstein
Liechtenstein annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Lithuania Annual Baseline
Lithuania
Lithuania annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Luxembourg Annual Baseline
Luxembourg
Luxembourg annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Latvia Annual Baseline
Latvia
Latvia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Malta Annual Baseline
Malta
Malta annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Netherlands Annual Baseline
Netherlands
Netherlands annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Norway FHI MSIS Statistics Bank
Norway
Norway FHI MSIS national monthly notifications from the official Allvis frontend API; adapter contract checks guard the unversioned endpoint.
ECDC Surveillance Atlas — Poland Annual Baseline
Poland
Poland annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Portugal Annual Baseline
Portugal
Portugal annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Romania Annual Baseline
Romania
Romania annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Sweden Public Health Agency SmiNet
Sweden
Sweden SmiNet national monthly reported cases from the official Public Health Agency statistics pages; public release is enabled with closed-month publication and revisable recent-month refreshes.
ECDC Surveillance Atlas — Slovenia Annual Baseline
Slovenia
Slovenia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Slovakia Annual Baseline
Slovakia
Slovakia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
US CDC NNDSS
United States
CDC National Notifiable Diseases Surveillance System provisional data.
US CDC NHSS HIV
United States
CDC NNDSS weekly data plus NHSS annual national HIV diagnoses