Risk factors for West Nile neuroinvasive disease and mortality in the United States, 2013-2024

West Nile virus (WNV) is the leading mosquito-borne infection in the United States and can cause West Nile fever (WNF) or West Nile neuroinvasive disease (WNND), resulting in substantial morbidity and mortality. Contemporary risk factor analyses are needed to identify populations at increased risk for severe outcomes and target interventions accordingly.

To assess risk factors for WNND and mortality among adults with WNV infection using a large national cohort from federated real-world data.

A retrospective cohort analysis from 2013-2024, consisting of de-identified electronic health record data from the TriNetX Research Network, including adult patients with an ICD-10 diagnosis consistent with WNV infection. Data were accessed from March 28^th to April 30^th, 2025.

The retrospective cohort included patients from 65 healthcare organizations from across the United States, using the TriNetX Research Network.

The overall initial cohort included 3,064 adult patients with an ICD-10 diagnosis consistent with WNV infection, including 1,328 with WNF and 1,206 with WNND.

Demographic characteristics (age, sex, race, ethnicity), comorbidities (hematologic malignancy, ischemic heart disease, other forms of heart disease, diabetes, HIV, chronic kidney disease (CKD), liver disease, hypertension, alcohol related disorders, cerebrovascular disease (CEVD), chronic obstructive pulmonary disease, asthma, multiple sclerosis, dementia, rheumatoid arthritis, organ transplant), and medications (immune suppressants, antineoplastics).

The primary outcomes were the development of WNND and all-cause mortality (30-day, 90-day, and overall mortality).

Among all patients diagnosed with WNV infection, those with WNND were older (mean age 59 vs 55, p-value <0.0001) and more often male (61% vs 48%, p-value <0.0001). Significant risk factors for WNND included age (adjusted hazard ratio [aHR] 1.11 per decade, 95% confidence interval [CI] 1.06-1.49), male sex (aHR 1.29, 1.15-1.45), CKD (aHR 1.21, 1.002-1.45), CEVD (aHR 1.22, 1.03-1.45), hematologic malignancy (aHR 1.38, 1.09-1.76), immune suppressant use (aHR 1.43, 1.11-1.83), hypertension (aHR 1.18, 1.04-1.34), alcohol related disorders (aHR 1.54, 1.20-1.97), and multiple sclerosis (aHR 2.3, 1.62-3.37). Significant risk factors for mortality were WNND (aHR 2.49 for 30-day mortality, 95% CI 1.37-4.52), age (aHR 1.32 per decade, 95% CI 1.07-1.60), CKD (aHR 2.08, 95% CI 1.01-3.93), and CEVD (aHR 2.00, 95% CI 1.14-3.50).

Risk factors for WNND broadly reflect impaired immune response and/or central nervous system vulnerability. Patients who developed WNND were at substantially increased risk of death. Targeted prevention strategies and countermeasures for those at greatest risk for WNND could substantially reduce morbidity and mortality.