Area health officials are asking residents to take caution after mosquito samples taken from several area cities tested positive for West Nile virus in recent months.

Mosquito samples taken in Southlake's Monticello neighborhood and in Northwest Colleyville's Jefferson Circle area tested positive for the virus in late June. A week later, samples taken in Grapevine near the lake and near Hall Johnson Road also tested positive.

Leaders say last year's drought followed by a mild winter and recent rainfall has made this a particularly bad season for West Nile. Human cases have been confirmed in Dallas, Denton, Parker and Tarrant counties.