Background . Since its introduction in 1999, West Nile virus has rapidly become the most common arboviral infection in North America. Little is known about the long-term clinical sequelae of West Nile virus infection.

Methods . A total of 49 patients with laboratory-confirmed West Nile virus infection were identified through state-based surveillance. Stratification for disease severity was based on hospitalization during the infection episode. Assessment occurred a mean of 13 months after diagnosis. Medical records were reviewed, and a complete neurologic examination was performed. Standardized surveys for quality of life, functional ability, fatigue, and depression were performed for all subjects. An extensive battery of neuropsychological tests was performed to assess cognitive function.

Results . Self-reported fatigue, memory problems, extremity weakness, word-finding difficulty, and headache were common complaints. Standardized survey data confirmed an overall sense of poor physical health, fatigue, depression, and moderate-to-severe disability in 24 (49%), 24 (49%), 12 (24%), and 4 (8%) patients, respectively. New tremor was seen or reported for 10 (20%) of the patients. Neuropsychological testing showed abnormalities of motor skills, attention, and executive functions. Univariate analysis of multiple risk factors did not identify any predictors of adverse outcomes.

Conclusions . Multiple somatic complaints, tremor, and abnormalities in motor skills and executive functions are common long-term problems among patients who have had West Nile virus infection. Patients with milder illness are just as likely as patients with more-severe illness to experience adverse outcomes.