There have been 11 cases of West Nile virus in South Carolina, including two in Rock Hill. South Carolina Department of Health and Environmental Control officials have now set mosquito traps for further testing within a two-mile area. The city will increase its mosquito spraying as a precaution on Friday. Officials will also treat any standing water where mosquitoes tend to breed. Crews began spraying for the most recent case near Baylor Drive in Rock Hill. Officials said about 80 percent of infected people do not show symptoms.