Sexually transmitted diseases (STDs), or sexually transmitted infections (STIs), are infections usually acquired though unprotected sexual contact with someone who's infected.

But, you can't always tell if someone is infected, because many STIs cause no symptoms. In fact, many people who have an STI don't know it.

That's why you have to be vigilant about STI prevention. Barrier methods of birth control, such as condoms, also help reduce your risk of getting most STIs. If you're sexually active, having just one partner who agrees to remain sexually exclusive with you can also help prevent STIs.

• Sexual health basics
• Women's sexual health

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Oct. 08, 2019