Neuroinvasive West Nile Virus Infection in Immunosuppressed and Immunocompetent Adults

Importance West Nile virus (WNV) is the leading cause of human arboviral disease in the US, peaking during summer. The incidence of WNV, including its neuroinvasive form (NWNV), is increasing, largely due to the expanding distribution of its vector, the Culex mosquito, and climatic changes causing heavy monsoon rains. However, the distinct characteristics and outcomes of NWNV in individuals who are immunosuppressed (IS) and individuals who are not IS remain underexplored. Objective To describe and compare clinical and radiographic features, treatment responses, and outcomes of NWNV infection in individuals who are IS and those who are not IS. Design, Setting, and Participants This retrospective cohort study used data from the Mayo Clinic Hospital system collected from July 2006 to December 2021. Participants were adult patients (age ≥18 years) with established diagnosis of NWNV infection. Data were analyzed from May 12, 2020, to July 20, 2023. Exposure Immunosuppresion. Main Outcomes and Measures Outcomes of interest were clinical and radiographic features and 90-day mortality among patients with and without IS. Results Of 115 participants with NWNV infection (mean SD age, 64 16 years; 75 66% male) enrolled, 72 (63%) were not IS and 43 (37%) were IS. Neurologic manifestations were meningoencephalitis (98 patients 85%), encephalitis (10 patients 9%), and myeloradiculitis (7 patients 6%). Patients without IS, compared with those with IS, more frequently reported headache (45 patients 63% vs 18 patients 42%) and myalgias (32 patients 44% vs 9 patients 21%). In contrast, patients with IS, compared with those without, had higher rates of altered mental status (33 patients 77% vs 41 patients 57%) and myoclonus (8 patients 19% vs 8 patients 4%). Magnetic resonance imaging revealed more frequent thalamic T2 fluid-attenuated inversion recovery hyperintensities in individuals with IS than those without (4 patients 11% vs 0 patients). Individuals with IS had more severe disease requiring higher rates of intensive care unit admission (26 patients 61% vs 24 patients 33%) and mechanical ventilation (24 patients 56% vs 22 patients 31%). The 90-day all-cause mortality rate was higher in the patients with IS compared with patients without IS (12 patients 28% vs 5 patients 7%), and this difference in mortality persisted after adjusting for Glasgow Coma Scale score (adjusted hazard ratio, 2.22; 95% CI, 1.07-4.27; P = .03). Individuals with IS were more likely to receive intravenous immunoglobulin than individuals without IS (12 individuals 17% vs 24 individuals 56%), but its use was not associated with survival (hazard ratio, 1.24; 95% CI, 0.50-3.09; P = .64). Conclusions and Relevance In this cohort study of individuals with NWNV infection, individuals with IS had a higher risk of disease complications and poor outcomes than individuals without IS, highlighting the need for innovative and effective therapies to improve outcomes in this high-risk population.