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West Nile virus

Last reviewed: 9 Apr 2025
Last updated: 07 Jan 2025

Summary

Definition

History and exam

Key diagnostic factors

  • fever of sudden onset
  • malaise
  • myalgia
  • arthralgia
  • pharyngitis
  • anorexia
  • abdominal pain
  • visual disturbances
  • headache
  • rash
  • lymphadenopathy
  • conjunctival injection
  • multifocal chorioretinal lesions
  • chorioretinitis and inflammatory vitritis
  • seizures
  • respiratory distress
  • jaundice
  • epigastric tenderness
  • mild confusion
  • disorientation
  • stupor/coma
  • neck stiffness
  • Kernig sign
  • Brudzinski sign
  • muscle paralysis
  • parkinsonism
  • ataxia
  • myoclonus
  • tremors
Full details

Other diagnostic factors

  • nausea/vomiting
  • generalized muscle weakness
  • splenomegaly
  • retinal hemorrhages
  • chest pain, dyspnea, palpitations
  • photophobia
  • depression
  • loss of memory
  • bowel and bladder dysfunction
  • cranial nerve palsies
Full details

Risk factors

  • living in/visiting areas with high West Nile virus activity
  • mosquito bites
  • blood transfusion
  • organ transplant
  • needlestick injuries
Full details

Diagnostic tests

1st tests to order

  • serology
  • plaque reduction neutralization test
  • cerebrospinal fluid (CSF) analysis
  • complete blood count
  • serum electrolytes
  • liver function tests
  • serum amylase/lipase
Full details

Tests to consider

  • MRI brain
  • CT head
  • reverse transcriptase-polymerase chain reaction (RT-PCR)
Full details

Treatment algorithm

ACUTE

West Nile fever

West Nile neuroinvasive disease

Contributors

Authors

Bruce Y. Lee, MD, MBA
Bruce Y. Lee

Professor of Health Policy and Management

Executive Director

Center for Advanced Technology and Communication for Health (CATCH)

Public Health Informatics Computational and Operation Research (PHICOR)

City University of New York (CUNY)

New York

NY

Disclosures

BYL declares that he has no competing interests.

Peer reviewers

Susan Stramer, PhD

Executive Scientific Officer

American Red Cross

Gaithersburg

MD

Disclosures

SS declares that she has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Hayes EB, Sejvar JJ, Zaki SR, et al. Virology, pathology, and clinical manifestations of West Nile virus disease. Emerg Infect Dis. 2005;11:1174-1179. Abstract

Centers for Disease Control and Prevention. West Nile virus: guidelines for West Nile virus surveillance and control. Jul 2024 [internet publication].Full text

Centers for Disease Control and Prevention. West Nile virus: West Nile virus disease therapeutics: review of the literature. May 2024 [internet publication].Full text

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
  • Differentials

    • Herpes simplex encephalitis
    • St. Louis encephalitis
    • Eastern equine encephalitis
    More Differentials
  • Guidelines

    • Guidelines for West Nile virus surveillance and control
    • Treatment and prevention of West Nile virus disease
    More Guidelines
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