West Nile Virus Symptoms and Treatment
West Nile virus (WNV) infection is primarily asymptomatic in approximately 80% of cases, with about 20% developing West Nile fever and less than 1% progressing to neuroinvasive disease with significant morbidity and mortality. 1, 2
Clinical Presentation
Asymptomatic Infection
West Nile Fever (Mild Form)
- Sudden onset of high fever (up to 104°F/40°C) 3
- Severe headache 3, 1
- Generalized myalgias and lumbosacral pain 3
- Anorexia, nausea, and vomiting 3
- Dizziness 3
- Bradycardia in relation to elevated body temperature (Faget's sign) 3
- Symptoms typically last approximately 3 days during the viremic period 3
- Most patients have an uneventful recovery 3, 2
Severe Disease (Neuroinvasive)
- Occurs in less than 1% of infected individuals 1, 2
- Recurrence of symptoms in more severe form within 48 hours following the initial viremic period 3
- Manifestations include:
- Clinical features include:
- Fever 3
- Nausea and vomiting 3
- Epigastric pain 3
- Jaundice 3
- Renal insufficiency 3
- Cardiovascular instability 3
- Bleeding diathesis (hematemesis, melena, metrorrhagia, hematuria, petechiae, ecchymoses, epistaxis, and gingival bleeding) 3
- Scleral and dermal icterus 3
- Epigastric tenderness without hepatic enlargement 3
Laboratory Findings
- Leukopenia may occur in the first week of illness 3
- Leukocytosis may develop during the second week 3
- Bleeding abnormalities with elevated prothrombin and partial thromboplastin times 3
- Decreased platelet count 3
- Presence of fibrin-split products 3
- Hyperbilirubinemia (may appear as early as day 3, typically peaks at end of first week) 3
- Elevated serum transaminase levels in severe hepatorenal disease (may remain elevated for up to 2 months) 3
Diagnosis
Primary Diagnostic Methods
- Serologic testing for virus-specific IgM and IgG antibodies in serum and/or CSF 3, 4
- IgM antibodies detectable 3-8 days after symptom onset, typically decreasing after 2-3 months (may persist up to 12 months) 3, 4
- Seroconversion between acute and convalescent sera (collected 7-10 days apart) strongly suggests recent WNV infection 3, 4
- Presence of anti-WNV IgM in CSF indicates CNS infection 3, 4
- Nucleic Acid Amplification Testing (NAAT) is more sensitive in immunosuppressed patients due to delayed immune response and prolonged viremia 3, 4
- Optimal specimens for NAAT include CSF, plasma, and serum 3, 4
Differential Diagnosis
- Viral hepatitis 3
- Malaria 3
- Leptospirosis 3
- Congo-Crimean hemorrhagic fever 3
- Rift Valley fever 3
- Typhoid 3
- Q fever 3
- Typhus 3
- Dengue hemorrhagic fever 3
- Other viral hemorrhagic fevers 3
Treatment
No FDA-approved specific antiviral therapy exists for WNV infection, and treatment is primarily supportive care. 4, 1, 5
Supportive Care
- Intravenous fluid administration 4
- Electrolyte supplementation 4
- Nutritional support 4
- Management of increased intracranial pressure in severe cases 1
- Respiratory support as needed 1
Special Considerations
- High-dose intravenous corticosteroids (methylprednisolone, 1g IV daily for 3-5 days) may be considered for acute disseminated encephalomyelitis (ADEM) associated with WNV 4
- EEG should be considered in patients with undiagnosed encephalopathy to rule out non-convulsive status epilepticus 3
Prognosis
- Mortality rate for neuroinvasive disease is approximately 10% overall 1
- Higher mortality (20%) in individuals 70 years or older 1
- Mortality increases to 30-40% in patients with hematologic malignancies, solid organ transplants, and those receiving B-cell-depleting monoclonal antibodies 1
- Among hospitalized patients, 30-40% require discharge to long-term care facilities 1
- More than 50% experience long-term sequelae including fatigue, weakness, myalgia, memory loss, and depression 1, 6