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 <i>Culex</i> 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.