To describe clinical and paraclinical markers and outcomes of neuroinvasive West Nile Virus (WNV), seen at an academic tertiary medical center in Chicago, IL in summer-autumn 2025.
WNV is a single-stranded RNA flavivirus that can cause neuroinvasive disease in 1% of patients. Overall mortality is 10%, but up to 40% in patients who are older than 70 and immunocompromised. Recurrent WNV outbreaks in the midwestern USA occur annually in summer and early autumn months with a neuroinvasive incidence of 0.9/100,000 WNV cases.
Single-institution case series.
Four patients (50% female) median age 72 years (range 68-87) presented with a viral prodrome followed by encephalopathy. All patients were either immunocompromised (post-lung-transplant n=1, chemotherapy n=2) and/or known malignancy (n=3).
All patients were diagnosed with WNV encephalitis; one with concomitant acute flaccid paralysis. One had confirmed electrographic seizures. MRI brain showed: no abnormalities (n=1), bilateral thalamic T2/FLAIR hyperintensities, (n=1), acute pontine infarct (n=1), and diffuse, bilateral T2/FLAIR hyperintensities of the mesial temporal lobes, thalami, cerebral peduncles, ventral spinal gray matter and gadolinium contrast-enhanced cauda equina (n=1).
Cerebrospinal fluid white cells were normal (4 cells/µL; n=1) or between 14-104 cells/µL (mixed pleocytosis; n=3). Two patients had CSF WNV IgG/IgM positivity. Two patients tested positive by CSF next generation metagenomic sequencing. All patients showed no improvement with multiple antimicrobials. Two patients were treated with intravenous immunoglobulin without improvement. All patients died in the hospital; median length of stay was 14 (8-23) days.