Severe West Nile virus disease in healthy adults

The inpatient records of 44 case patients with West Nile virus infection hospitalized in 2002 were reviewed. Sixty-five percent of the case patients had encephalitis, and 35% had aseptic meningitis. There was no significant difference in the distribution of aseptic meningitis versus encephalitis among adults aged less than or equal to50 years compared with adults aged greater than or equal to65 years. Focal weakness, likely due to anterior horn cell involvement, was present in 10 case patients ( overall rate, 23%; rate among patients with encephalitis, 34%). Case patients with focal weakness who were aged less than or equal to50 years had monoparesis, whereas those aged greater than or equal to65 years had paraparesis or quadriparesis. The overall mortality rate was 14%, and the mortality rate in patients aged greater than or equal to65 years was 35%. Increased age was associated with an increased mortality rate. The presence of paraparesis or quadriparesis was not independently predictive of mortality.