STD preventionBy Mayo Clinic staff
Sexually transmitted diseases (STDs) are infections acquired by sexual contact. You can get an STD by having unprotected sex with a partner who's infected. You can't always tell if someone is infected, however, because many STDs cause no symptoms, at least at first. In fact, a person may have an STD without knowing it.
That's why you have to be vigilant about STD prevention. If you're sexually active, your best bet for STD prevention is to have just one sex partner who doesn't have any STDs and who has sex only with you. If you're not in an exclusive relationship, you can still protect yourself by learning about and consistently practicing STD prevention, such as using condoms.