Snapshot A 60-year-old woman is brought into the emergency room for confusion and flaccid paralysis. Her family reveals that she recently made a trip to Asia and arrived home just a few days ago. On physical exam she is febrile and is not oriented to person, place, or time. She has hyperreflexia and flaccid paralysis of both legs. Cerebrospinal fluid analysis reveals elevated lymphocytes, normal protein, and normal glucose. Further analysis reveals immunoglobulin M to the suspected virus. Introduction Classification West Nile virus an enveloped, positive single-stranded RNA virus a flavivirus transmission mosquitoes Associated conditions West Nile fever meningoencephalitis Epidemiology Demographics more severe in the elderly more common in the young Risk factors mosquito bites ETIOLOGY Pathogenesis mosquito’s saliva transmits the virus to human blood virus then replicates in dendritic cells and spreads via lymphatics and bloodstream in some patients, the virus can invade the central nervous system and cause meningoencephalitis paralysis occurs when neurons are damaged in the anterior horn of the spinal cord Presentation Symptoms West Nile fever headache myalgias nausea and vomiting may develop a rash meningoencephalitis confusion coma acute headache photophobia nausea and vomiting Physical exam West Nile fever non-pruritic papular rash on trunk and extremities lymphadenopathy conjunctivitis meningoencephalitis acute flaccid paralysis myoclonus cerebellar ataxia seizures sensory is intact Studies Labs immunoglobulin M (IgM) enzyme-linked immunosorbent assay serum cerebrospinal fluid cerebrospinal fluid normal glucose ↑ or normal protein ↑ lymphocytes Making the diagnosis based on clinical presentation and laboratory studies Differential Dengue fever distinguishing factor characterized by mucosal bleeding, hemorrhage, and abdominal pain Treatment Management approach mainstay is supportive care Conservative supportive care indication all patients modalities fluids pain management mechanical ventilation Complications Rhabdomyolysis Guillain-Barré syndrome Prognosis Most infections are asymptomatic When symptomatic, the disease may progress to meningitis or encephalitis in < 1% of those infected