Long-Term Morbidity and Economic Burden of West Nile Virus Disease

BACKGROUND: Since 1999, over 36,000 cases of West Nile virus (WNV) disease have been reported in the United States, yet long-term morbidity and economic burden data for WNV disease are limited. We evaluated the morbidity and financial burden among WNV disease case-patients and control-patients approximately 2 years after their acute illness.

METHODS: We enrolled adult (age ≥18 years) Maricopa County residents tested for WNV disease during May–July 2010. Case-patients had laboratory-confirmed acute WNV disease; control-patients had an acute illness but negative test results for WNV infection. Symptoms during the 4 weeks before evaluation were assessed by using the CDC Symptom Inventory. Functional status was assessed using the Modified Medical Outcomes Survey Short-Form 36 (SF-36) and modified Rankin scale. We calculated costs incurred from medical appointments, additional care needs, and missed work. Categorical variables were compared by using chi-square or Fisher’s exact tests; continuous variables were compared using Wilcoxon tests.

RESULTS: We enrolled 22 case-patients and 22 control-patients. Median age among case-patients was 52 years (range: 28–81), compared with 48 years (range: 23–76) among control-patients (P=0.18); females constituted 68% of case-patients, compared with 46% of control-patients (P=0.12). Fourteen (64%) case-patients and 8 (36%) control-patients were hospitalized during their acute illness (P=0.07). No significant differences existed in the proportions of case-patients and control-patients reporting fatigue (38% vs 41%), muscle aches (43% vs 41%), joint pains (38% vs 27%), shortness of breath (15% vs 14%), depression (35% vs 23%), and problems with sleeping (30% vs 36%), memory (29% vs 31%), or concentration (32% vs 36%); control-patients were more likely to report headaches (55%) than case-patients (25%) (P=0.05). Median total SF-36 scores were similar between case-patients (80; interquartile range [IQR]: 42) and control-patients (82; IQR: 40) (P=0.42); there were also no differences in the 8 subset scores for functional health and well-being. A similar proportion of case-patients (82%) and control-patients (71%) reported no symptoms or no significant disability on the modified Rankin scale (P=0.48). Average costs incurred after acute illness were $8,397 (standard deviation [SD]: $13,725) for case-patients and $6,545 (SD: $17,042) for control-patients (P=0.14).

CONCLUSIONS: WNV disease case-patients did not have greater morbidity or costs during the 2 years after acute illness, compared with control-patients. Additional studies are warranted among larger cohorts and comparing WNV case-patients with healthy control-patients to better understand the long-term effects of WNV disease.