Morphology: Enveloped, single-stranded positive-sense RNA virus. Family Flaviviridae. Transmitted primarily by **Culex mosquitoes** (different vector from dengue/Zika/yellow fever). Bird reservoir; human + horse = dead-end hosts. Also transfusion + organ transplant transmission (donor screening).
Typical drugs
—
Empiric therapy when resistant
No specific antiviral. Supportive care; ICU for severe neuroinvasive disease.
Resistance notes
N/A.
Pearls
~80% asymptomatic; ~20% West Nile fever (febrile illness, headache, maculopapular rash); <1% neuroinvasive disease (encephalitis, meningitis, acute flaccid paralysis — mimics polio). Elderly + immunocompromised + transplant recipients at highest risk for neuroinvasive disease. Acute flaccid paralysis in summer → think WNV (also enterovirus EV-D68 in pediatrics). Diagnosis: WNV IgM in CSF or serum. No antiviral or vaccine for humans (equine vaccine exists). Donor screening prevents transfusion + transplant transmission. Supportive care: most encephalitis survivors have residual deficits.