Map of Texas counties with West Nile Virus.
Dallas is joining a list of North Texas cities that will use aerial spraying to combat the nation's worst outbreak of West Nile so far this year.
Mayor Mike Rawlings declared a state of emergency Wednesday. He said the city will begin the first aerial spraying of insecticide since 1966, when more than a dozen deaths were blamed on Encephalitis. Aerial spraying begins Thursday evening.