Abdominal Clues From a Neurotropic Virus: An Atypical West Nile Case Caught During a Fever of Unknown Origin Workup

West Nile virus (WNV) is a mosquito-borne ribonucleic acid (RNA) virus usually transmitted by Culex mosquitoes. While most infections are asymptomatic, WNV can cause severe neuroinvasive disease, including meningitis and encephalitis, with rare cases of seizures and strokes. Diagnosis typically involves detecting WNV-specific immunoglobulin M (IgM) antibodies or viral RNA. Management is supportive. This report details an unusual WNV presentation in a 50-year-old male patient with chronic lymphocytic leukemia (CLL) who experienced gastrointestinal symptoms and persistent high-grade fevers in early fall. This atypical presentation initially led to a diagnosis of pyrexia of unknown origin (PUO), delaying proper identification. The case highlights the importance of considering arboviral infections like WNV, especially during peak transmission months (July-September), to facilitate prompt diagnosis, reduce unnecessary investigations, and improve healthcare efficiency.