A sexually transmitted infection (STI) is caused by an organism (bacteria, virus, or parasite) that can be passed from one person to another during sex or intimate contact.
Most STIs are passed (or transmitted) between sexual partners through unprotected oral, vaginal (frontal) or anal sex. Some STIs are passed by skin-to-skin contact. Using condoms and other barriers for vaginal (frontal), oral and anal sex is a good way to lower the chances of passing many STIs.
If you are concerned that you might have an STI, get tested to find out for sure. Some STIs can cause serious health problems if left untreated. If your results come back positive (meaning you have an STI), your health care provider will tell you what kind of treatment you need. Some types of STIs can be cured with medication. Other STIs can be treated with medications, but not cured.