Chlamydia – CDC Fact Sheet (Detailed)

Basic Fact Sheet | Detailed Version

Detailed fact sheets are for healthcare providers and others with specific questions about sexually transmitted diseases (STDs). They include testing and treatment recommendations and citations, so the reader can research the topic more in depth.

What is chlamydia?

Chlamydia is a common STD caused by infection with Chlamydia trachomatis. It can cause cervicitis, urethritis, and proctitis.

In women, these infections can lead to:

Lymphogranuloma venereum (LGV) is another type of STD caused by C. trachomatis. LGV is the cause of recent proctitis outbreaks among gay, bisexual, and other men who have sex with men (MSM) worldwide.1,2

How common is chlamydia?

CDC estimates that there were four million chlamydial infections in 2018.3 Chlamydia is also the most frequently reported bacterial sexually transmitted infection in the United States.4 It is difficult to account for many cases of chlamydia. Most people with the infection have no symptoms and do not seek testing. Chlamydia is most common among young people. Two-thirds of new chlamydial infections occur among youth aged 15-24 years.3 Estimates show that 1 in 20 sexually active young women aged 14-24 years has chlamydia.5

Disparities persist among racial and ethnic minority groups. In 2019, chlamydia rates for African Americans/Blacks were nearly six times that of Whites.4 Chlamydia is also common among MSM. Among MSM screened for rectal chlamydial infection, positivity ranges from 3.0% to 10.5%.6,7 Among MSM screened for pharyngeal chlamydial infection, positivity has ranges from 0.5% to 2.3%.7.8

How do people get chlamydia?

Chlamydia spreads through vaginal, anal, or oral sex with someone with the infection. Semen does not have to be present to get or spread the infection.

Pregnant people can give chlamydia to their baby during childbirth. This can cause ophthalmia neonatorum (conjunctivitis) or pneumonia in some infants.9-12  Rectal or genital infection can persist one year or longer in infants infected at birth.13 However, sexual abuse should be a consideration among young children with vaginal, urethral, or rectal infection beyond the neonatal period.

People treated for chlamydia can get the infection again if they have sex with a person with chlamydia.14

Who is at risk for chlamydia?

Sexually active people can get chlamydia through vaginal, anal, or oral sex without a condom with a partner who has chlamydia. It is a very common STD, especially among young people.3

Sexually active young people are at high risk of getting chlamydia for behavioral, biological, and cultural reasons. Some don’t always use condoms.15 Some may move from one monogamous relationship to another during the likely infectivity period of chlamydia. This can increase the risk of transmission.16 Teenage girls and young women may have cervical ectopy (where cells from the endocervix are present on the ectocervix).17 Cervical ectopy may increase susceptibility to chlamydial infection. High chlamydia prevalence among young people also may reflect barriers to accessing STD prevention services. These barriers can include lack of transportation, cost, and perceived stigma.16-20

MSM are also at risk for infection since chlamydia can spread by oral or anal sex. Among MSM screened for rectal infection, positivity ranges from 3.0% to 10.5%.6.7 Among MSM screened for pharyngeal infection, positivity ranges from 0.5% to 2.3%.7.8

What are the symptoms of chlamydia?

Some refer to chlamydia as a “silent” infection. This is because most people with the infection have no symptoms or abnormal physical exam findings. Studies find that the proportion of people with chlamydia who develop symptoms vary by setting and study methodology. Two modeling studies estimate that about 10% of men and 5-30% of women with a confirmed infection develop symptoms.21.22 The incubation period of chlamydia is unclear. Given the relatively slow replication cycle of the organism, symptoms may not appear until several weeks after exposure in people who develop symptoms.

In women, the bacteria initially infect the cervix. This may cause signs and symptoms of cervicitis (e.g., mucopurulent endocervical discharge, easily induced endocervical bleeding). It also can infect the urethra. This may cause signs and symptoms of urethritis (e.g., pyuria, dysuria, urinary frequency). Infection can spread from the cervix to the upper reproductive tract (i.e., uterus, fallopian tubes), causing PID. PID may be asymptomatic (“subclinical PID”)23 or acute, with typical symptoms of abdominal and/or pelvic pain. Signs of cervical motion tenderness and uterine or adnexal tenderness also may occur during examination.

Men with symptoms typically have urethritis, with a mucoid or watery urethral discharge and dysuria. Some men develop epididymitis (with or without symptomatic urethritis) with unilateral testicular pain, tenderness, and swelling.24

Chlamydia can infect the rectum in men and women. This can happen either directly (through receptive anal sex), or via spread from the cervix and vagina in a woman.25, 26 While these infections often have no symptoms, they can cause symptoms of proctitis (e.g., rectal pain, discharge, and/or bleeding).26-28

Conjunctivitis can occur in both men and women through contact with infected genital secretions.29

While chlamydia can also spread to the throat by having oral sex, there are typically no symptoms. It also does not appear to be an important cause of pharyngitis.26

What health problems can result from chlamydia?

The initial damage that chlamydia causes is often unnoticed. However, infections can lead to serious health problems with both short- and long-term effects.

If a woman does not receive treatment, chlamydia can spread into the uterus or fallopian tubes, causing PID. Symptomatic PID occurs in about 10-15% of women who do not receive treatment.30,31 However, chlamydia can also cause subclinical inflammation of the upper genital tract (“subclinical PID”). Both acute and subclinical PID can cause long-term damage to the fallopian tubes, uterus, and surrounding tissues. The damage can lead to chronic pelvic pain, tubal factor infertility, and potentially fatal ectopic pregnancy.32,33

Some patients with PID develop perihepatitis, or “Fitz-Hugh-Curtis Syndrome”. This syndrome includes inflammation of the liver capsule and surrounding peritoneum, which can cause right upper quadrant pain.

In pregnant people, untreated chlamydia can lead to pre-term delivery,34 ophthalmia neonatorum (conjunctivitis), and pneumonia in the newborn.

Reactive arthritis can occur in men and women, following infection with or without symptoms. This is sometimes part of a triad of symptoms (with urethritis and conjunctivitis) formerly referred to as Reiter’s Syndrome.35

What about chlamydia and HIV?

Untreated chlamydia may increase a person’s chances of getting or transmitting HIV.36

How does chlamydia affect a pregnant person and their baby?

In newborns, untreated chlamydia can cause:

  • pre-term delivery,34
  • ophthalmia neonatorum (conjunctivitis),
  • and pneumonia.

Prospective studies show that chlamydial conjunctivitis and pneumonia occur in 18-44% and 3-16%, respectively, of infants born to those with chlamydia. 9-12 Neonatal prophylaxis against gonococcal conjunctivitis routinely performed at birth does not effectively prevent chlamydial conjunctivitis.37-39

Screening for and treating chlamydia in pregnant people is the best way to prevent disease in infants. At the first prenatal visit and during the third trimester, screen:

  • All pregnant people under age 25; and
  • All pregnant people 25 years and older at increased risk for chlamydia (e.g., those who have a new or more than one sex partner).

Retest those with infection four weeks and three months after they complete treatment.40

Who to test for chlamydia?

Anyone with the following genital symptoms should not have sex until they see a healthcare provider:

  • A discharge
  • A burning sensation when peeing
  • Unusual sores, or a rash

Anyone having oral, anal, or vaginal sex with a partner recently diagnosed with an STD should see a healthcare provider.

Because chlamydia usually has no symptoms, screening is necessary to identify most infections. Screening programs can reduce rates of adverse sequelae in women.31,41 CDC recommends yearly chlamydia screening of all sexually active women younger than 25. CDC also recommends screening for older women with risk factors, such as new or multiple partners, or a sex partner who has a sexually transmitted infection.40 Screen and treat those who are pregnant as noted in “How does chlamydia affect a pregnant person and their baby?” Women who are sexually active should discuss their risk factors with a healthcare provider to determine if more frequent screening is necessary.

Routine screening is not necessary for men. However, consider screening sexually active young men in clinical settings with a high prevalence of chlamydia. This can include adolescent clinics, correctional facilities, and STD clinics. Consider this when resources permit and do not hinder screening efforts in women.40

Screen sexually active MSM who have insertive intercourse for urethral chlamydial infection. Also screen MSM who have receptive anal intercourse for rectal infection at least yearly. Screening for pharyngeal infection is not recommended. MSM, including those with HIV, should receive more frequent chlamydia screening at 3- to 6-month intervals, if risk behaviors persist or if they or their sexual partners have multiple partners.40

At the initial HIV care visit, providers should test all sexually active people for chlamydia. Test at least each year during HIV care. A patient’s healthcare provider might determine more frequent screening is necessary, based on the patient’s risk factors.42

How is chlamydia diagnosed?

Diagnose chlamydia with nucleic acid amplification tests (NAATs), cell culture, and other types of tests. NAATs are the most sensitive tests to use on easy-to-obtain specimens. This includes vaginal swabs (either clinician- or patient-collected) or urine.43

To diagnose genital chlamydia in women using a NAAT, vaginal swabs are the optimal specimen. Urine is the specimen of choice for men. Urine is an effective alternative specimen type for women.43 Self-collected vaginal swab specimens perform as well as other approved specimens using NAATs.44 Patients may prefer self-collected vaginal swabs or urine-based screening to more invasive specimen collection.45 Adolescent girls may be good candidates for self-collected vaginal swab- or urine-based screening.

Diagnose rectal or pharyngeal infection by testing at the anatomic exposure site. While useful for these specimens, culture is not widely available. Additionally, NAATs have better sensitivity and specificity compared with culture for detecting C. trachomatis at non-genital sites.46-48 Most tests, including NAATs, are not FDA-cleared for use with rectal or pharyngeal swab specimens. NAATs have better sensitivity and specificity compared with culture for the detection of C. trachomatis at rectal sites.46-48  However, some laboratories have met set requirements and have validated NAAT testing on rectal and pharyngeal swab specimens.

What is the treatment for chlamydia?

Antibiotics can easily cure chlamydia. Treatment options are the same, whether a person also has HIV or not.

Patients treated with single-dose antibiotics should not have sex for seven days. Patients treated with a seven-day course of antibiotics should not have sex until they complete treatment, and their symptoms are gone. This helps prevent spreading the infection to sex partners. It is important to take all medicine prescribed to cure chlamydia. Medicine should not be shared with anyone. Although treatment will cure the infection, it will not repair any long-term damage done by the disease. If a person’s symptoms continue for more than a few days after receiving treatment, a healthcare provider should reevaluate them.

Repeat infection with chlamydia is common.49 Women whose sex partners do not receive appropriate treatment are at high risk for re-infection. Having multiple chlamydial infections increases a woman’s risk of serious reproductive health problems (e.g., PID and ectopic pregnancy).50,51 A healthcare provider should retest those with chlamydia about three months after treatment of an initial infection. Retesting is necessary even if their partners receive successful treatment.40

Infants with chlamydia may develop conjunctivitis and/or pneumonia.10 Healthcare providers can treat infection in infants with antibiotics.

What about partners?

People treated for chlamydia should tell their recent sex partners so the partner can see a healthcare provider. “Recent” partners include anyone the patient had anal, vaginal, or oral sex with in the 60 days before symptom onset or diagnosis. This will help protect the partner from health problems and prevent re-infection.

Patients treated with single-dose antibiotics should not have sex for seven days. Patients treated with a seven-day course of antibiotics should not have sex until they complete treatment, and their symptoms go away.

For tips on talking to partners about sex and STD testing, visit www.gytnow.org/talking-to-your-partner/external icon

In some states, healthcare providers may give people with chlamydia extra medicine or prescriptions to give to their sex partner(s). This is called “expedited partner therapy”, or “EPT.” Clinical trials comparing EPT to asking the patient to refer their partners in for treatment find that EPT leads to fewer re-infections in the index patient and more partner treatment.52 EPT is another strategy providers use to manage the partners of people with chlamydial infection. Partners should still seek medical care, regardless of whether they receive EPT. For more information about EPT, including the legal status in a specific area, see Legal Status of Expedited Partner Therapy.

How can chlamydia be prevented?

Condoms, when used correctly, every time someone has sex can reduce the risk of getting or giving chlamydia.53 The only way to completely avoid chlamydia is to not have vaginal, anal, and oral sex. Another option is being in a long-term, mutually monogamous relationship with a partner who has been tested and does not have chlamydia.

National Network of STD Clinical Prevention Training Centers

National Network of STD Clinical Prevention Training Centers, STD Clinical Consultation Networkexternal icon

Healthcare providers can contact the STD Clinical Consultation Network (STDCCN) for convenient, free clinical support. The National Network of STD Clinical Prevention Training Centers provides this service and operates five days a week. More information is available at https://www.stdccn.org/render/Publicexternal icon.

Division of STD Prevention (DSTDP)
Centers for Disease Control and Prevention
www.cdc.gov/std

CDC-INFO Contact Center
1-800-CDC-INFO (1-800-232-4636)
TTY: (888) 232-6348
Contact CDC-INFO

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E-mail: npin-info@cdc.gov

American Sexual Health Association (ASHA)external icon
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References

1. O’Farrell N, Morison L, Moodley P, et al. Genital ulcers and concomitant complaints in men attending a sexually transmitted infections clinic: implications for sexually transmitted infections management. Sexually transmitted diseases 2008;35:545-9.

2. White JA. Manifestations and management of lymphogranuloma venereum. Current opinion in infectious diseases 2009;22:57-66.

3. Kreisel KM, Spicknall IH, Gargano JW, Lewis FM, Lewis RM, Markowitz LE, Roberts H, Satcher Johnson A, Song R, St. Cyr SB, Weston EJ, Torrone EA, Weinstock HS. Sexually transmitted infections among US women and men: Prevalence and incidence estimates, 2018. Sex Transm Dis 2021; in press.

4. CDC. Sexually Transmitted Disease Surveillance, 2019. Atlanta, GA: Department of Health and Human Services; April 2021.

5. Torrone E, Papp J, Weinstock H. Prevalence of Chlamydia trachomatis Genital Infection Among Persons Aged 14–39 Years — United States, 2007–2012. MMWR 2014;63:834-8.

6. Marcus JL, Bernstein KT, Stephens SC, et al. Sentinel surveillance of rectal chlamydia and gonorrhea among males–San Francisco, 2005-2008. Sexually transmitted diseases 2010;37:59-61.

7. Pinsky L, Chiarilli DB, Klausner JD, et al. Rates of asymptomatic nonurethral gonorrhea and chlamydia in a population of university men who have sex with men. Journal of American college health : J of ACH 2012;60:481-4.

8. Park J, Marcus JL, Pandori M, Snell A, Philip SS, Bernstein KT. Sentinel surveillance for pharyngeal chlamydia and gonorrhea among men who have sex with men–San Francisco, 2010. Sexually transmitted diseases 2012;39:482-4.

9. Frommell GT, Rothenberg R, Wang S, McIntosh K. Chlamydial infection of mothers and their infants. The Journal of pediatrics 1979;95:28-32.

10. Hammerschlag MR, Chandler JW, Alexander ER, English M, Koutsky L. Longitudinal studies on chlamydial infections in the first year of life. Pediatric infectious disease 1982;1:395-401.

11. Heggie AD, Lumicao GG, Stuart LA, Gyves MT. Chlamydia trachomatis infection in mothers and infants. A prospective study. American journal of diseases of children (1960) 1981;135:507-11.

12. Schachter J, Grossman M, Sweet RL, Holt J, Jordan C, Bishop E. Prospective study of perinatal transmission of Chlamydia trachomatis. JAMA : the journal of the American Medical Association 1986;255:3374-7.

13. Bell TA, Stamm WE, Wang SP, Kuo CC, Holmes KK, Grayston JT. Chronic Chlamydia trachomatis infections in infants. JAMA : the journal of the American Medical Association 1992;267:400-2.

14. Batteiger BE, Tu W, Ofner S, et al. Repeated Chlamydia trachomatis genital infections in adolescent women. The Journal of infectious diseases 2010;201:42-51.

15. Eaton DK, Kann L, Kinchen S, et al. Youth risk behavior surveillance – United States, 2011. Morbidity and mortality weekly report Surveillance summaries (Washington, DC : 2002) 2012;61:1-162.

16. Kraut-Becher JR, Aral SO. Gap length: an important factor in sexually transmitted disease transmission. Sexually transmitted diseases 2003;30:221-5.

17. Singer A. The uterine cervix from adolescence to the menopause. British journal of obstetrics and gynaecology 1975;82:81-99.

18. Cunningham SD, Kerrigan DL, Jennings JM, Ellen JM. Relationships between perceived STD-related stigma, STD-related shame and STD screening among a household sample of adolescents. Perspectives on sexual and reproductive health 2009;41:225-30.

19. Elliott BA, Larson JT. Adolescents in mid-sized and rural communities: foregone care, perceived barriers, and risk factors. The Journal of adolescent health : official publication of the Society for Adolescent Medicine 2004;35:303-9.

20. Tilson EC, Sanchez V, Ford CL, et al. Barriers to asymptomatic screening and other STD services for adolescents and young adults: focus group discussions. BMC public health 2004;4:21.

21. Farley TA, Cohen DA, Elkins W. Asymptomatic sexually transmitted diseases: the case for screening. Preventive medicine 2003;36:502-9.

22. Korenromp EL, Sudaryo MK, de Vlas SJ, et al. What proportion of episodes of gonorrhoea and chlamydia becomes symptomatic? International journal of STD & AIDS 2002;13:91-101.

23. Wiesenfeld HC, Sweet RL, Ness RB, Krohn MA, Amortegui AJ, Hillier SL. Comparison of acute and subclinical pelvic inflammatory disease. Sexually transmitted diseases 2005;32:400-5.

24. Berger RE, Alexander ER, Monda GD, Ansell J, McCormick G, Holmes KK. Chlamydia trachomatis as a cause of acute “idiopathic” epididymitis. The New England journal of medicine 1978;298:301-4.

25. Barry PM, Kent CK, Philip SS, Klausner JD. Results of a program to test women for rectal chlamydia and gonorrhea. Obstetrics and gynecology 2010;115:753-9.

26. Jones RB, Rabinovitch RA, Katz BP, et al. Chlamydia trachomatis in the pharynx and rectum of heterosexual patients at risk for genital infection. Annals of internal medicine 1985;102:757-62.

27. Quinn TC, Goodell SE, Mkrtichian E, et al. Chlamydia trachomatis proctitis. The New England journal of medicine 1981;305:195-200.

28. Thompson CI, MacAulay AJ, Smith IW. Chlamydia trachomatis infections in the female rectums. Genitourinary medicine 1989;65:269-73.

29. Kalayoglu MV. Ocular chlamydial infections: pathogenesis and emerging treatment strategies. Current drug targets Infectious disorders 2002;2:85-91.

30. Haggerty CL, Gottlieb SL, Taylor BD, Low N, Xu F, Ness RB. Risk of sequelae after Chlamydia trachomatis genital infection in women. The Journal of infectious diseases 2010;201 Suppl 2:S134-55.

31. Oakeshott P, Kerry S, Aghaizu A, et al. Randomized controlled trial of screening for Chlamydia trachomatis to prevent pelvic inflammatory disease: the POPI (prevention of pelvic infection) trial. BMJ (Clinical research ed) 2010;340:c1642.

32. Cates W, Jr., Wasserheit JN. Genital chlamydial infections: epidemiology and reproductive sequelae. American journal of obstetrics and gynecology 1991;164:1771-81.

33. Westrom L, Joesoef R, Reynolds G, Hagdu A, Thompson SE. Pelvic inflammatory disease and fertility. A cohort study of 1,844 women with laparoscopically verified disease and 657 control women with normal laparoscopic results. Sexually transmitted diseases 1992;19:185-92.

34. Rours GI, Duijts L, Moll HA, et al. Chlamydia trachomatis infection during pregnancy associated with preterm delivery: a population-based prospective cohort study. European journal of epidemiology 2011;26:493-502.

35. Carter JD, Inman RD. Chlamydia-induced reactive arthritis: hidden in plain sight? Best practice & research Clinical rheumatology 2011;25:359-74.

36. Fleming DT, Wasserheit JN. From epidemiological synergy to public health policy and practice: the contribution of other sexually transmitted diseases to sexual transmission of HIV infection. Sexually transmitted infections 1999;75:3-17.

37. Bell TA, Sandstrom KI, Gravett MG, et al. Comparison of ophthalmic silver nitrate solution and erythromycin ointment for prevention of natally acquired Chlamydia trachomatis. Sexually transmitted diseases 1987;14:195-200.

38. Chen JY. Prophylaxis of ophthalmia neonatorum: comparison of silver nitrate, tetracycline, erythromycin and no prophylaxis. The Pediatric infectious disease journal 1992;11:1026-30.

39. Isenberg SJ, Apt L, Wood M. A controlled trial of povidone-iodine as prophylaxis against ophthalmia neonatorum. The New England journal of medicine 1995;332:562-6.

40. Workowski, KA, Bachmann, LH, Chang, PA, et. al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep 2021; 70(No. 4): 1-187.

41. Scholes D, Stergachis A, Heidrich FE, Andrilla H, Holmes KK, Stamm WE. Prevention of pelvic inflammatory disease by screening for cervical chlamydial infection. The New England journal of medicine 1996;334:1362-6.

42. CDC. Incorporating HIV prevention into the medical care of persons living with HIV. Recommendations of CDC, the Health Resources and Services Administration, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. MMWR Recommendations and reports : Morbidity and mortality weekly report Recommendations and reports / Centers for Disease Control 2003;52:1-24.

43. APHL. Laboratory Diagnostic Testing for Chlamydia trachomatis and Neisseria gonorrhoeae. Expert Consultation Meeting Summary Report. January 13-15, 2009. Atlanta, GA.

44. Schachter J, Chernesky MA, Willis DE, et al. Vaginal swabs are the specimens of choice when screening for Chlamydia trachomatis and Neisseria gonorrhoeae: results from a multicenter evaluation of the APTIMA assays for both infections. Sexually transmitted diseases 2005;32:725-8.

45. Doshi JS, Power J, Allen E. Acceptability of chlamydia screening using self-taken vaginal swabs. International journal of STD & AIDS 2008;19:507-9.

46. Bachmann LH, Johnson RE, Cheng H, et al. Nucleic acid amplification tests for diagnosis of Neisseria gonorrhoeae and Chlamydia trachomatis rectal infections. Journal of clinical microbiology 2010;48:1827-32.

47. Mimiaga MJ, Mayer KH, Reisner SL, et al. Asymptomatic gonorrhea and chlamydial infections detected by nucleic acid amplification tests among Boston area men who have sex with men. Sexually transmitted diseases 2008;35:495-8.

48. Schachter J, Moncada J, Liska S, Shayevich C, Klausner JD. Nucleic acid amplification tests in the diagnosis of chlamydial and gonococcal infections of the oropharynx and rectum in men who have sex with men. Sexually transmitted diseases 2008;35:637-42.

49. Hosenfeld CB, Workowski KA, Berman S, et al. Repeat infection with Chlamydia and gonorrhea among females: a systematic review of the literature. Sexually transmitted diseases 2009;36:478-89.

50. Hillis SD, Owens LM, Marchbanks PA, Amsterdam LF, Mac Kenzie WR. Recurrent chlamydial infections increase the risks of hospitalization for ectopic pregnancy and pelvic inflammatory disease. American journal of obstetrics and gynecology 1997;176:103-7.

51. Bakken IJ, Skjeldestad FE, Lydersen S, Nordbo SA. Births and ectopic pregnancies in a large cohort of women tested for Chlamydia trachomatis. Sexually transmitted diseases 2007;34:739-43.

52. Trelle S, Shang A, Nartey L, Cassell JA, Low N. Improved effectiveness of partner notification for patients with sexually transmitted infections: systematic review. BMJ (Clinical research ed) 2007;334:354.

53. Holmes KK, Levine R, Weaver M. Effectiveness of condoms in preventing sexually transmitted infections. Bulletin of the World Health Organization 2004;82:454-61.