Every year nearly 9 million people under the age of 25 get a new STI (sexually transmitted infection).¹ One of these infections is chlamydia. If you've had sex, you could have an STI. Some STIs cause symptoms. Others don't. You could have one and not know it. Some STIs make you sick today and others can cause problems later in life. These include serious problems like cancer or infertility. Some can even kill you.

What is chlamydia and how do you get it?
Chlamydia is the most common bacterial STI.¹ You get it from having sex with an infected person. Babies can get it from their mothers during childbirth. Although most infected people have no symptoms, they can still pass on chlamydia.

Am I safe if I only have oral or anal sex?
Chlamydia can also be passed during oral^{2, 3} or anal^{2, 4} sex.

What happens if I'm infected?
If you are like most people, you will have no symptoms at all. On the other hand, you could have symptoms such as pain when going to the bathroom or a "discharge" coming from your penis or vagina. If you are a female, you may have abdominal pain. This could be from pelvic inflammatory disease (PID), caused by chlamydia. PID can interfere with your ability to get pregnant.⁵ Chlamydia also increases your chance of getting HIV.

How do you treat chlamydia?
Chlamydia can be treated with antibiotics. Delayed treatment can result in serious problems. Both you and your partner must be treated.

Am I safe if I always use a condom?
If you always use condoms for vaginal sex, you can cut your chance of getting chlamydia by about half.^6,7 And, there is some evidence that if you always use condoms for anal sex, you can reduce your chance of rectal chlamydia.⁸ However, at this point, there is no evidence that condoms reduce your chance of getting chlamydia during oral sex.

What can I do to avoid getting infected?
Avoid sexual activity if you are single. Be faithful to one uninfected partner for the rest of your life. Already had sex? See a doctor and get checked.

References
1 Weinstock H, Berman S, Cates W Jr. Sexually transmitted diseases among American youth: incidence and prevalence estimates, 2000. Perspect Sex Reprod Health; 2004;36(1):6-10.
2 Stamm WE. Chlamydia trachomatis infections of the adult. In: Holmes KK, Mardh PA, Sparling PF, et al., eds. Sexually Transmitted Diseases. 3rd ed. New York, NY: McGraw Hill, Co.; 1999:407-422.
3 Edwards S, Carne C. Oral sex and transmission of non-viral STIs. Sex Transm Infect. 1998 Apr;74(2):95-100.
4 Manavi K, McMillan A, Young H. The prevalence of rectal chlamydial infection amongst men who have sex with men attending the genitourinary medicine clinic in Edinburgh. Int J STD AIDS. 2004 Mar;15(3):162-4.
5 Westrom L, Eschenbach D. Pelvic inflammatory disease. In: Holmes KK, et al, eds. Sexually Transmitted Diseases. 3rd ed. New York: McGraw-Hill; 1999:783-809.
6 Ahmed S, Lutalo T, Wawer M, et al. HIV incidence and sexually transmitted disease prevalence associated with condom use: a population study in Rakai, Uganda. AIDS. 2001;15(16):2171-2179.
7 Baeten JM, Nyange PM, Richardson BA, et al. Hormonal contraception and risk of sexually transmitted disease acquisition: results from a prospective study. Am J Obstet Gynecol. 2001;185(2):380-385.
8 Hocking J, Fairly CK. Associations between condom use and rectal or urethral chlamydia infection in men. Sex Transm Dis. 2006;33(4)256-8.

Authored by: Sheetal Malhotra, MBBS, MS
Date: May 2007
Reviewed by: Jennifer A. Shuford, MD, MPH
Date: July 2009