Sexually transmitted infections (STIs) are infections that are spread by sexual contact. STIs can cause severe damage to your body—even death. Except for colds and flu, STIs are the most common contagious (easily spread) infections in the United States, with millions of new cases each year. Although some STIs can be treated and cured, others cannot.
A person with an STI can pass it to others by contact with skin, genitals, mouth, rectum, or body fluids. Anyone who has sexual contact—vaginal, anal, or oral sex—with another person may get an STI. STIs may not cause symptoms. Even if there are no symptoms, your health can be affected.
STIs are caused by bacterial or viral infections. STIs caused by bacteria are treated with antibiotics. Those caused by viruses cannot be cured, but symptoms can be treated.
The following factors increase the risk of getting STIs:
- More than one sexual partner
- A partner who has or has had more than one sexual partner
- Sex with someone who has an STI
- History of STIs
- Use of intravenous drugs (injected into a vein) or partner use of intravenous drugs
- Chlamydia (see FAQ071 Chlamydia, Gonorrhea, and Syphilis)
- Gonorrhea (see FAQ071 Chlamydia, Gonorrhea, and Syphilis)
- Genital herpes (see FAQ054 Genital Herpes)
- Human immunodeficiency virus (HIV) infection (see PFS005 Testing for Human Immunodeficiency Virus)
- Human papillomavirus (HPV) infection (see FAQ191 Human Papillomavirus [HPV] Vaccination)
- Syphilis (see FAQ071 Chlamydia, Gonorrhea, and Syphilis)
- Trichomoniasis (see FAQ028 Vaginitis)
- Hepatitis B (see FAQ125 Protecting Yourself Against Hepatitis B and Hepatitis C)
There are many ways you can reduce your risk of getting an STI:
- Know your sexual partners and limit their number—Your partner’s sexual history is as important as your own. The more partners you or your partners have, the higher your risk of getting an STI.
- Use a latex condom—Using a latex condom every time you have vaginal, oral, or anal sex decreases the chances of infection. Condoms lubricated with spermicides do not offer extra protection. Frequent use of some spermicides can increase the risk of HIV.
- Avoid risky sex practices—Sexual acts that tear or break the skin carry a higher risk of STIs. Even small cuts that do not bleed let germs pass back and forth. Anal sex poses a high risk because tissues in the rectum tear easily. Body fluids also can carry STIs. Having any unprotected sexual contact with an infected person poses a high risk of getting an STI.
- Get immunized—Vaccinations are available that will help prevent hepatitis B and some types of HPV (see FAQ191 Human Papillomavirus [HPV] Vaccination and FAQ125 Protecting Yourself Against Hepatitis B and Hepatitis C).
Having an STI during pregnancy can harm the fetus. Gonorrhea and chlamydia both can cause health problems in the infant ranging from eye infections to pneumonia. Syphilis may cause miscarriage or stillbirth. HIV infection can pass to a baby during a vaginal birth.