"Many of them were surprised, too. Sexually transmitted diseases affect at least 40 million Americans. But often the person infected with an STD doesn't have any symptoms and can spread the disease without knowing it. Most STDs can be cured. All can be prevented. If you are sexually active, find out how you can protect yourself and your partner. Get the answers you need from your doctor, your local health department, or the National STD Hotline of the U.S. Centers for Disease Control (1-800-227-8922), Because there are some surprises you don't want."