Chlamydia is the most common sexually transmitted infection (STI) in North America and Europe. It is caused by the bacteria Chlamydia trachomatis. This STI is more and more frequent and the number of cases has been increasing over the past fifteen years. In the United States, more than 2.8 cases are reported each year. In 3/4 of cases, this STI affect adolescents and young adults aged 15 to 24 years.

This infection is difficult to diagnose because the majority of infected people have no symptoms and therefore do not seek medical attention. People infected with gonococcus, the bacteria that causes gonorrhea, are often infected with chlamydia as well. This is why screening for these two diseases should be done systematically.

Although the infection is easy to treat, it can lead to serious health problems if it is not caught and treated early.

Causes of Chlamydia

Chlamydia is spread through unprotected oral, anal, or vaginal sex, the exchange of sex toys, the exchange of body fluids, and contact with mucous membranes. It is rarely transmitted through cunnilingus.

Chlamydia can also be passed to a newborn baby from an infected mother during childbirth.

Possible complications

In women, untreated chlamydia can spread from the vagina to the uterus, and sometimes to the tubes. It then causes inflammatory infectious pelvic disease. This can then lead to infertility, increase the risk of ectopic pregnancies and be responsible for chronic pelvic pain.

In men, chlamydia can cause inflammation of the prostate (infectious prostatitis) or testes (orchi-epididymitis), which can lead to infertility.

In rarer cases, the infection spreads to the joints through the bloodstream, causing inflammation in both sexes. This is the Fiessinger-Leroy-Reiter syndrome.

Chlamydia infection increases the risk of transmitting HIV. When a newborn baby is infected by his or her mother during childbirth, he or her may later get an infection of the lungs (pneumonia) or of the eyes (conjunctivitis).

When to see a doctor?

If you have had unsafe, unprotected sex, you should see your doctor for screening tests.

Chlamydia is often referred to as a “silent disease” because more than 50% of infected men and 70% of women have no symptoms and are unaware that they have it. Symptoms usually appear after a few weeks, but may take even longer to appear.

Symptoms of Chlamydia

In women

  • Most often, no sign;
  • Burning sensation when urinating;
  • Unusual vaginal discharge;
  • Bleeding between periods, or during or after sex;
  • Pain during sex;
  • Lower abdominal pain or lower back pain;
  • Proctitis (inflammation of the wall of the rectum);
  • Abnormal discharge from the anus.

In men

  • Sometimes no sign;
  • Tingling, itching in the urethra (duct at the outlet of the bladder which opens at the end of the penis);
  • Abnormal discharge from urethra, rather clear and somewhat milky;
  • Burning when urinating;
  • Pain and sometimes swelling in the testicles, in some cases;
  • Proctitis (inflammation of the wall of the rectum);
  • Abnormal discharge from the anus.
  • In the newborn child to whom the mother transmits chlamidiae
  • Eye infection with redness and discharge there;
  • Lung infection which can lead to coughing, difficult breathing and fever.

In the newborn child to whom the mother transmits chlamydia

  • Eye infection with redness and discharge;
  • Lung infection which can lead to coughing, difficult breathing and fever.

Risk factors

  • Having more than one sexual partner;
  • Having a partner who has other sexual partners;
  • Not using a condom;
  • Having contracted an STI in the past.
  • Being between 15 and 29 years old.
  • Being HIV positive
  • Having a surrogate mother for chlamydia (for an unborn child).


Using condoms helps prevent the transmission of chlamydia during anal or vaginal sex. Condoms or dental dams can also be used as a means of protection during oral sex.

Regular screening allows for prompt treatment and prevents transmission of infection to new partners. With a positive result, it is important to tell anyone you have had sex with who may have been exposed. They will need to be tested and treated immediately if infected. This is extremely important, as this infection is not immune and can be caught several times in a row. However, in 84% of cases, a person who suffers a new contamination gets it from the same person as the first time!

Chlamydia can be detected in both men and women with a simple test.
The first urine sample is taken from a man, and from a woman, the first urine sample is taken or a vulvovaginal self-collection is performed.
Other samples are possible, from the opening of the urethra, the cervix (with a pelvic examination) as well as self-samples from the rectum, or a sample from the throat.

Medical treatments

Chlamydia is treated with antibiotics. Current recommendations are treatment with:

  • oral azithromycin in a single dose of 1 gram prescribed as a priority.
  • doxycycline 100 mg by mouth, morning and evening, for a week. It has more side effects and has the downside that it can be forgotten.

The partner(s) must also be treated. Sex should be avoided for at least a week or the partners should use a condom. Checking for other STIs is also essential and the person treated should see their doctor no later than 7 days after starting treatment.

In 10 to 15% of cases, even well-treated infection persists. This is why two screening tests should be performed again, approximately 5 weeks after the end of treatment and between 3 and 6 months after the end of treatment.

Chlamydia is the most common STI in the US. Often it does not produce any symptoms and is therefore still too often “underdiagnosed”. These long-term consequences, especially on fertility, are however dramatic. Remember that simple, non-invasive urine tests are readily available and allow rapid diagnosis. And remember that you can get infected again if your partner hasn’t been treated.

Franck Saebring

Franck Saebring is a family man first and a writer second. Born and raised in Frankfurt, Germany, only cars eclipse his love of gadgets. His very passionate about anything tech and science related.