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Sexually transmitted diseases (also known as STDs — or STIs for "sexually transmitted infections") are infectious diseases that spread from person to person through intimate contact. STDs can affect guys and girls of all ages and backgrounds who are having sex — it doesn't matter if they're rich or poor.

Unfortunately, STDs have become common among teens. Because teens are more at risk for getting some STDs, it's important to learn what you can do to protect yourself.

STDs are more than just an embarrassment. They're a serious health problem. If untreated, some STDs can cause permanent damage, such as infertility (the inability to have a baby) and even death (in the case of HIV/AIDS).

How STDs Spread

One reason STDs spread is because people think they need to have sexual intercourse to become infected. That's wrong. A person can get some STDs, like herpes or genital warts, through skin-to-skin contact with an infected area or sore.

Another myth about STDs is that you can't get them if you have oral or anal sex. That's also wrong because the viruses or bacteria that cause STDs can enter the body through tiny cuts or tears in the mouth and anus, as well as the genitals.

STDs also spread easily because you can't tell whether someone has an infection. In fact, some people with STDs don't even know that they have them. These people are in danger of passing an infection on to their sex partners without even realizing it.

Some of the things that increase a person's chances of getting an STD are:

•  Sexual activity at a young age. The younger a person starts having sex, the greater his or her chances of becoming infected with an STD.
•  Lots of sex partners. People who have sexual contact — not just intercourse, but any form of intimate activity — with many different partners are more at risk than those who stay with the same partner.
•  Unprotected sex. Latex condoms are the only form of birth control that reduce your risk of getting an STD. Spermicides, diaphragms, and other birth control methods may help prevent pregnancy, but they don't protect a person against STDs.