HARTFORD, Conn. (AP) - Five more Connecticut residents have tested positive for West Nile virus, bringing the total to 15 human cases this season.

Department of Public Health Commissioner Dr. Raul Pino on Thursday said all five became ill in early to mid-September.

He called it "very unusual" to have this many people seriously ill with the infection in early to mid-September. He urged residents to continue taking precautions to prevent mosquito bites, especially with warm weather in the forecast.

Three of the new cases are residents of Danbury, Norwalk and Stamford. One patient is from Thompson and another is from Westbrook. Their ages range from 40 years old to over 70. Three required hospitalization.

The Connecticut Agriculture Experiment Station expects to find infected mosquitoes until the first hard frost in October.