West Nile virus

Last reviewed: 22 Aug 2023
Last updated: 10 Aug 2023



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
More key diagnostic factors

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
Other diagnostic factors

Risk factors

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

Diagnostic investigations

1st investigations to order

  • serology
  • cerebrospinal fluid (CSF) analysis
  • complete blood count
  • serum electrolytes
  • liver function tests
  • serum amylase/lipase
More 1st investigations to order

Investigations to consider

  • MRI brain
  • CT head
  • viral culture or reverse transcriptase-polymerase chain reaction (RT-PCR)
More investigations to consider

Treatment algorithm


West Nile fever

West Nile neuroinvasive disease



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



BYL declares that he has no competing interests.

Peer reviewers

Susan Stramer, PhD

Executive Scientific Officer

American Red Cross




SS declares that she has no competing interests.

  • Differentials

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    • Eastern equine encephalitis
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  • Guidelines

    • West Nile virus: information for healthcare providers
    • West Nile virus surveillance and control guidelines
    More Guidelines
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