West Nile Virus (WNV) Infection and Encephalitis (WNE) Clinical Presentation

Updated: Apr 05, 2021
  • Author: David J Cennimo, MD, FAAP, FACP, FIDSA, AAHIVS; Chief Editor: Michael Stuart Bronze, MD  more...
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Patients with West Nile virus (WNV) infection may or may not report a mosquito bite history, although the higher frequency of bites results in a higher probability of encountering the virus. The incubation period is typically 2-6 days but may range up to 14 days and may be longer in immunocompromised patients. [22, 23]  West Nile encephalitis (WNE) may start with constitutional symptoms, including the nonspecific symptoms of West Nile fever (eg, fever, headaches, muscle aches, joint pain, vomiting). Clinically, WNE is indistinguishable from other forms of viral aseptic meningitis. [22]

Neuroinvasive disease manifests as fever and neurologic symptoms. A meningeal-type infection may manifest as typical meningeal symptoms (eg, neck stiffness, photophobia, headache). [15, 22] Encephalitis may be more varied, possibly featuring mental status changes, confusion, lethargy, seizures, local paresthesia, and/or movement disorders. [15, 22] These can manifest as extrapyramidal symptoms—coarse tremor, myoclonus, parkinsonian features such as bradykinesia, rigidity, and postural instability. [15, 22]

In children and adolescents, neuroinvasive WNV disease most commonly manifests as meningitis-type symptoms; however, encephalitis-type symptoms are more common in older adults and elderly individuals. [24]


Physical Examination

Most patients with symptomatic WNV infection are febrile.

Neurologic examination findings may vary depending on the severity and manifestations of the disease. The presence of Kernig or Brudzinski signs may indicate meningeal irritation in patients with meningitis. Tremor, either fine or coarse, may be encountered. Mental status is likely to be depressed in patients with encephalitis and can manifest as subtle increased sleepiness to frank coma. Confusion or neurocognitive signs may be present. Acute flaccid paralysis results in a poliomyelitis-like loss of tone and strength and may affect one or more extremities.

Examination findings may be remarkable for diffuse maculopapular rash.

Ocular findings may include chorioretinitis featuring “target-like” lesions, retinal hemorrhages, and vitreitis. [25, 26, 27]