West Nile virus (WNV) is an arbovirus in the family Flaviviridae. It is the primary cause of arboviral disease in the United States. Most (80% of cases) are asymptomatic. It is spread by the bite of local mosquitoes. There was a large outbreak in Texas in 2012, primarily in Dallas. Although WNV is now endemic in most of the US, regional outbreaks can occur at any time. The map below from the CDC demonstrates the wide range of disease in October 2018.