West Nile Virus

West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States.

In 2004, a total of 36 states reported 1,053 cases of human WNV illness to CDC. Of these, 326 cases were reported from California, 316 cases were reported from Arizona, and 141 cases were reported from Colorado.

A total of 588 of the 1,053 cases occurred in males; the median age of patients was 51 years. Illness onset ranged from April 23 to August 24; a total of 28 cases were fatal.