Chlamydia is one of the most common sexually transmitted diseases, often referred to as STDs or STIs, impacting hundreds of thousands of people every year. While chlamydia can be easily treated for most people, it regularly goes without being detected thanks to its symptoms, which may not appear for all people who are infected or which may be confused for other issues.

What causes chlamydia, what does it do to the body, how common is it, and how can it be prevented? Use this guide to learn all that and more.

In This Section

  • Chlamydia Symptoms
  • Chlamydia Transmission
  • Chlamydia Prevalence
  • At-Risk Groups
  • Chlamydia Complications
  • Chlamydia & Pregnancy
  • Chlamydia Testing
  • Chlamydia Treatment
  • Chlamydia Prevention

Chlamydia Symptoms

Chlamydia is a sexually transmitted disease that’s caused by the bacteria Chlamydia trachomatis. It infects both men and women, though most people who become infected, male or female, don’t show any obvious physical signs of the disease.

In addition to being difficult and confusing to diagnose via a visual examination, chlamydia also isn’t as well-understood as other STDs when it comes to the infection’s incubation period. Studies have shown a variable infection window of 5 to 14 days. Because of this, many people who do become symptomatic don’t make the connection between a possible exposure to chlamydia and development of physical signs.

All of this makes chlamydia tough to fight and easy to spread, and for these reasons, it’s often said that chlamydia is a “silent” infection. But research has indicated that about 10% of men and as many as 30% of women with chlamydia develop symptoms, and these may vary depending on the sex of the individual as well as the location of the infection. Chlamydia can infect the genitals and/or the anus, as well as the eyes.

Male

  • Watery or milky discharge from penis
  • Painful urination
  • Swelling or pain in one or both testicles
  • Anal pain, itching, bleeding, discharge and/or swelling
  • Diarrhea
  • Redness, discharge or itching in eyes

Female

  • Discolored and/or foul-smelling vaginal discharge
  • Vaginal swelling
  • Pain during sex
  • Burning or painful sensation when urinating
  • More frequent urination
  • Abdominal or lower back pain
  • Nausea
  • Low-grade fever
  • Bleeding between periods or after vaginal sex
  • Anal pain, itching, bleeding, discharge and/or swelling
  • Diarrhea
  • Redness, discharge or itching in eyes

Chlamydia Transmission

Chlamydia is spread through intimate contact with an infected partner, including contact with the penis, vagina, mouth or anus of a person who is infected with the disease. Chlamydia is transmitted through exposure of mucous membranes, such as those inside the vagina or anus, to secretions or other fluids from a person who is infected. It is possible though less common for chlamydia to be spread during oral sex because the Chlamydia trachomatis bacteria prefers to inhabit the genitals and anus.

Fully penetrative sex need not occur for infection to take place; all that’s needed is contact of the vagina, cervix, anus, penis or mouth with the infected bodily fluids of another person. Similarly, chlamydia infections of the eye can occur if fluids contact the eye during sex or afterward, such as through hand-to-eye contact.

Chlamydia also can be passed to a newborn during birth, but it cannot be spread through intimate contact like kissing or holding hands or through casual contact like shaking hands or sharing food or drinks.

Chlamydia Prevalence

Among STDs that are reported to federal health officials, which includes chlamydia, gonorrhea (the clap), syphilis, HIV and others, chlamydia is by far the most common.

In 2018 alone, the federal Centers for Disease Control and Prevention estimate that nearly 1.8 million people were infected with chlamydia in the U.S. This compares to about 115,000 people who had syphilis and about 580,000 who had gonorrhea.

The number of chlamydia infections reported in the U.S. has risen for the past five consecutive years and in 24 of the past 25 years. Even after adjusting for the changes in the overall population during that time, the chlamydia rate has surged by more than 180% since 1994.

Chlamydia infections per 100,000 people by year

1994 192.5
1995 187.8
1996 190.6
1997 205.5
1998 231.8
1999 247.2
2000 251.4
2001 274.5
2002 289.4
2003 301.7
2004 316.5
2005 329.4
2006 344.3
2007 367.5
2008 398.1
2009 405.3
2010 423.6
2011 453.4
2012 453.3
2013 443.5
2014 452.2
2015 475
2016 494.7
2017 524.6
2018 539.9

Among the states, chlamydia is most common in Alaska, where it occurs at a rate of 832.5 per 100,000. It’s least common in West Virginia, a state with a population-adjusted chlamydia rate of 198.2 per 100,000.

Chlamydia infections per 100,000 people by state

Alaska 832.5
Louisiana 774.8
Mississippi 740.1
South Carolina 674.9
New Mexico 670.5
North Carolina 647.8
Georgia 632.2
Delaware 627.7
Illinois 604
New York 602.4
Arkansas 587.9
Maryland 586.3
California 585.3
Nevada 584
Alabama 583.4
Arizona 581.6
Tennessee 569
Missouri 568.1
Oklahoma 559
Ohio 542.3
Hawaii 541.8
Indiana 523.9
Colorado 519.4
Rhode Island 517.8
Texas 517.6
South Dakota 509.6
Michigan 507.8
Virginia 507.3
Florida 499.2
Kansas 488.5
Wisconsin 483.6
Montana 468.1
Iowa 466.7
North Dakota 466.6
Connecticut 466.3
Washington 465.2
Oregon 464
Pennsylvania 463.4
Massachusetts 444
Kentucky 436.4
Minnesota 422.6
Nebraska 418
New Jersey 405.5
Idaho 382.8
Wyoming 374.4
Utah 339.8
Maine 325.2
New Hampshire 278.1
Vermont 274.5
West Virginia 198.2

At-Risk Groups

Any person who is sexually active, even if they don’t have penetrative sex to completion, could become infected with chlamydia if they have contact with an infected partner. However, chlamydia is far more common among young people, who are generally less likely to use condoms consistently or to cycle through relationships more quickly than older people.

It’s estimated that as many as 1 in 20 sexually active young women is infected with chlamydia, and prevalence is higher among women than men, though men who have sex with men may be at an elevated risk when compared to men who don’t. Chlamydia is much more common in women until about age 35, when the prevalence shifts to men having higher rates.

Chlamydia infections per 100,000 people by age and sex

Age group Male Female
10-14 13.6 92.9
15-19 959 3,306.8
20-24 1,784.5 4,064.6
25-29 1,134.7 1,726.2
30-34 651.3 750.2
35-39 370.4 363.9
40-44 216.5 176.6
45-54 115.1 66
55-64 41.8 18.5
65+ 7.4 2.3
Total 380.6 692.7

Among racial and ethnic groups, African-Americans have the highest rates of chlamydia, while Asians have the lowest reported population-adjusted rates of the STD.

Chlamydia infections per 100,000 people by race or ethnicity

African-Americans 1,192.50
Native Americans/Alaska Natives 784.8
Native Hawaiians 700.8
Hispanics 392.6
Whites 212.1
Multirace 184.9
Asians 132.1

Chlamydia Complications

While chlamydia doesn’t carry the same short- or long-term health risks of other STDs, such as syphilis or HIV, which can be deadly if untreated, in some cases chlamydia can be just as risky. Undiagnosed and untreated chlamydia can cause serious health complications in both men and women, including:

  • Other STDs: People with chlamydia are at elevated risk of having other STDs, including gonorrhea and HIV.
  • Pelvic inflammatory disease: PID is an infection of the reproductive system that occurs in as many as 15% of women with untreated chlamydia. PID causes inflammation of the uterus, fallopian tubes, ovaries and cervix, and some cases can impact a woman’s fertility by causing permanent damage to these structures.
  • Pregnancy complications: Untreated chlamydia can contribute to preterm delivery as well as infections in newborns.
  • Reactive arthritis: Both men and women who have had chlamydia are at a higher risk of developing reactive arthritis, a condition formerly called Reiter’s Syndrome.
  • Epididymitis: Chlamydia can inflame a coiled tube near the testicle, which can cause fever, swelling and pain.

Chlamydia & Pregnancy

Women with untreated chlamydia have a higher rate of preterm delivery, meaning having a baby that is premature, and their babies are more likely to be born with conjunctivitis as well as pneumonia as a result of traveling through the birth canal of a person with chlamydia.

Studies have indicated that as many as 44% of babies born to women with untreated cervical chlamydia had conjunctivitis at birth, and as many as 16% had pneumonia. The most common method of preventing conjunctivitis, ocular prophylaxis administered at birth, which is recommended for all newborns, is not effective against conjunctivitis caused by chlamydia.

That’s why pregnant women under 25 should be screened for chlamydia at their first prenatal visit, and some should be screened again during their pregnancy. Antibiotics used to treat chlamydia should not cause complications during pregnancy, so women who test positive can be treated successfully in almost all cases.

Chlamydia Testing

Because chlamydia so infrequently results in any noticeable physical symptoms, every sexually active person should get checked for the STD at least once in their lifetimes. Anybody who has recently had sexual contact with a person who is positive, or any sexually active person who notices any of the physical signs of the disease should also speak with their healthcare provider about getting tested.

Here are the federal recommendations for chlamydia testing:

  • Young women: Sexually active women under 25 should get checked for chlamydia at least once a year. Those who test positive should be tested again about three months after completing treatment.
  • All women: Women who are older than 25 and engage in sex with multiple and/or new partners should also be screened about once a year.
  • Pregnant women: Those under 25 should be screened at their initial prenatal visit, as should those over 25 who are at increased risk of the disease (multiple or new sexual partners). Both groups also should be screened again during their third trimester.
  • Men: Annual screening is recommended for men who are in high-risk populations, such as gay and bisexual men, and high-risk individuals should consider screening every 3 to 6 months.
  • HIV-positive individuals: Annual screening for chlamydia is recommended for sexually active individuals who have tested positive for HIV.

Few cases of chlamydia can be diagnosed because most people don’t have symptoms, and it’s common for those who do display symptoms to have physical signs that can easily be mistaken for another condition or health problem.

The good news is that a number of tests exist for positively identifying chlamydia, including those that are done on cell cultures, vaginal swabs or urine tests. Generally, vaginal swabs are preferred for diagnosing chlamydia in women, while urine samples is the ideal specimen for men.

Several options are available when it comes to where and how you can get screened for chlamydia (and other STDs). These include:

  • Doctor’s office
  • Urgent care center
  • Pharmacy clinic
  • Campus health clinic
  • Planned Parenthood
  • Community health clinics
  • At-home test kits

Chlamydia Treatment

Chlamydia is easily cured with antibiotics. People who test positive for the STD will often take a single dose, though some doctors may recommend a 7-day course of antibiotics. People who are undergoing treatment for chlamydia should refrain from having sex or doing any other sexual activities for at least a week to prevent the spread of chlamydia to partners.

Standard treatment protocols call for people to receive a single oral dose of azithromycin or a 7-day course of twice-daily doxycycline. Alternative treatment regimens include erythromycin, levofloxacin or ofloxacin.

Newborns who develop chlamydia-related complications also should be treated with antibiotics.

It’s important to note that successful treatment will clear the body of an active chlamydia infection, but it won’t undo any permanent damage that may have been done to the body, nor will it inoculate the individual against future infections, and repeat chlamydia infections are common. Those who have been successfully treated should be tested again about three months later to ensure no further infection is present.

Chlamydia Prevention

While chlamydia is easily treated, the best cure for any STD is prevention. Of course, the only way to ensure you won’t be at risk of any STDs, including chlamydia, is to abstain from any intimate contact, but condoms and dental dams can greatly reduce the risk of contracting or spreading chlamydia. Remember, too, that it’s possible to transmit chlamydia even without having vaginal, oral or anal sex to completion.

Everyone who is sexually active should be screened at least once for chlamydia, and for high-risk groups, screening should be done more often. This has a two-fold benefit: It prevents health complications due to unchecked chlamydia, but it also helps prevent the accidental spread of this STD.

If you have received treatment for chlamydia, all your past and present partners should be informed so they also can be tested (and treated if necessary). Engaging in monogamous sexual relationships with people who have tested negative for chlamydia is another way to reduce your risk, as those who have multiple partners or regularly have new sexual partners are at elevated risk of chlamydia.

Conclusion

While it’s true that chlamydia is an incredibly common STD that’s growing even more common, the good news is that this STD is very easily treated. But it’s important to get tested and treated and to engage in smart preventive habits because if it’s left untreated, chlamydia can do serious, lasting damage to your body.

Additional References