The Florida Department of Health issued a health alert Friday. Mosquito control is inspecting and treating properties in the affected areas.
Health officials say the eleven cases are connected to the Rio and Jensen Beach area. Seven are from Martin County and four are St. Lucie County residents.
Dengue is sometimes called "break bone fever" because of the severe joint pain it causes in extreme cases. Other symptoms include high fever, severe headache and a rash.
Residents are advised to drain standing water and to cover skin with clothing or repellent.