Arthropod-borne viruses (arboviruses) are transmitted to humans primarily 
through the bites of infected mosquitoes and ticks. West Nile virus (WNV) is the 
leading cause of domestically acquired arboviral disease in the United States. 
However, several other arboviruses also cause sporadic cases and seasonal 
outbreaks of neuroinvasive disease (i.e., meningitis, encephalitis, and acute 
flaccid paralysis). This report summarizes surveillance data reported to CDC in 
2013 for WNV and other nationally notifiable arboviruses, excluding dengue. 
Forty-seven states and the District of Columbia reported 2,469 cases of WNV 
disease. Of these, 1,267 (51%) were classified as WNV neuroinvasive disease, for 
a national incidence of 0.40 per 100,000 population. After WNV, the next most 
commonly reported cause of arboviral disease was La Crosse virus (LACV) (85 
cases), followed by Jamestown Canyon virus (JCV), Powassan virus (POWV), and 
eastern equine encephalitis virus (EEEV) (eight). WNV and other arboviruses 
continue to cause serious illness in substantial numbers of persons annually. 
Maintaining surveillance remains important to help direct and promote prevention 
activities.