Abstract Details

Title Neuroinvasive West Nile: Epidemiology & Fatal Encephalitis Series from Chicago, Summer 2025

Topic Infectious Disease

Presentation(s) P11 - Poster Session 11 (11:45 AM-12:45 PM)

Poster/Presentation
Number 3-011

Objective To describe West Nile virus (WNV) epidemiology and report a series of four fatal neuroinvasive cases.

Background WNV is the leading cause of arboviral neuroinvasive disease in the United States. Cook County, Illinois ranks among the top WNV-burdened areas, contributing 6.3% of all CDC-reported neuroinvasive cases from 1999–2022. Seroprevalence data suggest that fewer than 1% of infections become neuroinvasive, yet these cases dominate surveillance; true infection rates are 50–100× higher than reported. Most cases occur in persons aged ≥50 years and peak in late summer, when WNV amplifies in a bird–mosquito–bird cycle involving passerines (crows, robins, & jays). Neuroinvasive WNV mortality approaches 9%, with nearly half of cases requiring ICU admission. No official guidelines exist for WNV in immunocompromised patients; management relies on vector avoidance and supportive therapy in severe infection.

Design/Methods We reviewed publicly available surveillance data from the CDC ArboNET Surveillance System and Cook County Department of Public Health. Four cases are detailed as follows:

Results Four patients (ages 69–87; 3 male, 1 female) with CSF WNV IgM positivity were cared for in a tertiary hospital ICU setting in September, 2025. Two patients were immunocompromised secondary to malignancy with chemotherapy or lung transplant. Approximately one week of nonspecific flu-like symptoms preceded presentation before all patients became acutely encephalopathic, requiring intubation and mechanical ventilation for airway protection. Neuroimaging findings included bilateral thalamic hyperintensities on MRI. Three developed worsening leukopenia with secondary pulmonary and bloodstream infections, two with fungemia, requiring broad-spectrum empiric treatment. Two received IVIG without significant clinical benefit. All died during hospitalization (mean, 20 days).

Conclusions WNV has high mortality in elderly and immunocompromised patients who commonly reside in urban high-risk centers like Chicago. IVIG has been used anecdotally but lacks proven efficacy in the treatment of neuroinvasive WNV. Prevention of WNV through public and provider awareness and robust vector control remains paramount.

Authors/Disclosures
Jon Klein PRESENTER	Mr. Klein has nothing to disclose.
Diann George, MD	Dr. George has nothing to disclose.
Ruben J. Mylvaganam, MD	Dr. Mylvaganam has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for United Therapeutics. Dr. Mylvaganam has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Janssen Pharmaceuticals. Dr. Mylvaganam has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Roivant Sciences. Dr. Mylvaganam has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for United Therapeutics. Dr. Mylvaganam has received personal compensation in the range of $500-$4,999 for serving as a Fellowship Director with United Therapeutics.

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