West Nile virus

West Nile virus (WNV) is a neurotropic mosquito-borne virus belonging to the Flaviviridae family ^[1]. The virus was first identified in Uganda in 1937 and later spread globally, with notable emergence in Europe and North America ^[2][1][3]. Available source material characterizes it as an important zoonotic pathogen in which mosquitoes act as vectors and birds serve as amplifying hosts ^[1].

In humans, WNV infection can be asymptomatic or present as a mild febrile illness, and asymptomatic infection is described as frequent ^[3]. A smaller proportion of cases progress to neuroinvasive disease, including meningitis and encephalitis, and severe outcomes such as paralysis and death are reported rarely ^[1][3]. The sources also note that recovery may be prolonged in some cases ^[3]. Source-backed detail on incubation period, specific neurologic sequelae beyond those named, and complication frequency is not yet available.

Historically, epidemics were described in Europe, Africa, the Middle East, and parts of Asia, with later expansion to North America in the late 1990s ^[3]. More recent reviews describe continued geographic expansion, particularly into temperate regions of Europe and North America, with climate-related factors such as milder winters and longer warm seasons cited as contributors ^[2][1]. The virus circulates in an enzootic cycle and has caused periodic outbreaks in Europe, where increased human exposure has been linked to regional spread ^[1]. WNV is also described as responsible for substantial morbidity and mortality in birds, horses, and humans ^[3].

Transmission is primarily mosquito-borne: mosquitoes act as vectors, and humans and other mammals are infected through mosquito bites ^[1]. The reviewed sources describe an enzootic cycle in which birds are amplifying hosts, supporting sustained circulation between vectors and avian reservoirs ^[1]. Climate conditions that increase mosquito activity and allow overwintering within mosquito populations may facilitate year-round transmission ^[2].

The source material does not provide a detailed, consistent risk-group profile beyond exposure through mosquito bites and the role of birds and mosquitoes in transmission ^[1]. It does note that severe neuroinvasive disease can occur and that management is particularly relevant for severe neurologic cases ^[2][3]. Because the snippets do not specify age, occupation, comorbidity, or pregnancy-related risk patterns, source-backed detail on high-risk groups is not yet available.

No approved human vaccine is available in the source material, so prevention and management depend heavily on exposure control and vector control ^[2][3]. The reviewed literature emphasizes mosquito-control strategies, including genetically modified mosquitoes and novel insecticides, as important tools ^[2]. Adaptive public-health strategies are also highlighted as necessary because climate change and urbanization are altering vector behavior and transmission dynamics ^[2].

In surveillance settings, WNV should be interpreted as a zoonotic, mosquito-borne pathogen with an enzootic bird–mosquito cycle and periodic spillover to humans ^[1]. Monitoring is especially important in regions where climate conditions extend mosquito seasons or support overwintering, because these factors may increase transmission risk and outbreak potential ^[2]. The available sources indicate that WNV is a significant public-health concern in multiple regions, but source-backed detail on standardized case definitions or routine laboratory thresholds is not yet available ^[2][3].

1. 1 Simonin Y et al. Circulation of West Nile Virus and Usutu Virus in Europe: Overview and Challenges. Viruses. 2024 Apr 12. PMID: 38675940. doi: 10.3390/v16040599. PubMed: https://pubmed.ncbi.nlm.nih.gov/38675940/
2. 2 Singh 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/
3. 3 Rossi 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/
4. 4 West Nile virus. Journal of Equine Veterinary Science. 2000. doi: 10.1016/s0737-0806(00)70214-0. DOI: https://doi.org/10.1016/s0737-0806(00)70214-0
5. 5 West Nile Virus. Pediatric Practice Guidelines. 2020. doi: 10.1891/9780826185235.0012s. DOI: https://doi.org/10.1891/9780826185235.0012s
6. 6 West Nile Virus. Red Book Atlas of Pediatric Infectious Diseases. 2023. doi: 10.1542/9781610026314-164. DOI: https://doi.org/10.1542/9781610026314-164

ICD-10

ICD-11

Total cases

275

Peak month

2021-10

Coverage

6 reporting countries · 2000-01-01 → 2022-10-22