Spraying for mosquitoes is under way tonight in several Brooklyn areas. The spraying will continue until 6 a.m. Friday morning. Targeted areas include parts of Canarsie, East Flatbush, Flatlands, Georgetown, Marine Park, Mills Basin, Mills Island, Spring Creek, Starrett City and Georgetown. Fliers papering blocks in the area are giving residents the heads up about the pesticide application. Health officials say no one in Brooklyn has contracted the mosquito-borne West Nile virus yet this season, and they hope that spraying pest-prone areas will keep it that way.