What are STIs?

Sexually transmitted infections (STIs) are passed from someone who has an infection to someone who doesn’t, mainly through person-to-person sexual contact.

Most people with an STI don’t show any signs. The only way to know for sure is to get tested. If you are sexually active, the most effective way to prevent STIs is to protect yourself.

Different bacteria, viruses, and parasites cause more than 30 kinds of STIs. Use the links below to learn the facts about STIs, including symptoms and available treatments.