Identifying risks for severity of neurological symptoms in Hungarian West Nile virus patients

BACKGROUND: West Nile virus (WNV) infections have become increasingly prevalent in certain European countries, including Hungary. Although most human infections do not cause severe symptoms, in approximately 1% of cases WNV infections can lead to severe WNV neuroinvasive disease (WNND) and death. The goal of our study was to assess the neurological status changes of WNV –infected patients admitted to inpatient care and to identify potential risk factors as underlying reasons for severe neurological outcome. METHODS: We conducted a retrospective chart review of 66 WNV-infected patients from four Hungarian medical centers. Patients’ neurological status at hospital admission and at two follow-up intervals (1st follow-up, within 60–90 days and 2nd follow-up, within 150–180 days, after hospital discharge) were assessed. All of the 66 patients in the initial sample had some type of neurological symptoms and 56 patients were diagnosed with WNND. The modified Rankin Scale (mRS) and the West Nile Virus Neurological Index (WNV-N Index), a scoring system designed for the purpose of this study, were used for neurological status assessment. Patients were dichotomized into two categories, “moderately severe” and “severe” based on their neurological status. Descriptive analysis for sample description, stratified analysis for calculation of odds ratio (OR) and logistic regression for continuous input variables, were performed. RESULTS: The average number of days between the onset of neurological symptoms and hospital admission (the neurological symptom interval) was 6.01 days. Complications during the hospital stay arose in almost a fifth of the patients (18.2%) and 5 patients died. Each day’s increase in the neurological symptom interval significantly increased the risk for developing a severe neurological status following hospital admission (0.799-fold and 0.688-fold, based on the WNV-N Index and mRS, respectively). Patients’ age, comorbidity, presence of complications and symptoms of malaise, and gait uncertainty were shown to be independent risk factors for severe neurological status. CONCLUSIONS: Timely hospital admission of patients with neurological symptoms as well as risk assessment by clinicians - possibly with an optimal assessment tool for estimating neurological status- could improve the neurological outcome of WNV-infected patients.