Risk Factors and Causes of Chlamydia

Chlamydia is a highly prevalent STD today. Let's see what causes it and who is most at risk of catching it.
Risk Factors and Causes of Chlamydia

Last update: 18 June, 2021

Chlamydia has been one of the most common sexually transmitted diseases (STDs) for decades. The European Center for Disease Prevention and Control (ECDC) estimates that 250,000 cases a year occur in Europe alone. According to the World Health Organization (WHO) this figure reaches 130 million when contextualized across the planet. So, in order to prevent this disease, we need to get to know the causes of chlamydia.

Despite the fact that it’s a simple disease to cure, the absence of symptoms isn’t uncommon in many patients. This makes it rather difficult to diagnose, leads to new infections, and increases the chances of complications (such as infertility). Today we’ll be focusing on the mechanisms that cause chlamydia, as well as its risk factors.

Causes of chlamydia

Causes of chlamydia include an infection
Chlamydia trachomatis, the bacteria that causes chlamydia, is capable of producing various alterations in the body.

Chlamydia is caused by the bacteria Chlamydia trachomatis. According to some publications, this is part of a group made up of a total of 12 intracellular bacteria, three of which can infect humans (C. trachomatis, C. pneumoniae and C. psitacci). The latter is responsible for other types of infections too.

Let’s go back to the particular variety that concerns us – Chlamydia trachomatis. Experts have found that it causes different conditions according to the serovar (subgroup) the bacterium belongs to. The most common are the following:

  • A, B, Ba, and C: These can cause trachoma, a contagious eye disease.
  • D and K: These are related to sexually transmitted diseases (STDs), especially those located on the surface of the mucosa.
  • L1, L2 and L3: These produce sexually transmitted diseases capable of developing hemorrhagic proctocolitis and lymphogranuloma venereum.

C. trachomatis causes clinical conditions similar to those of the bacterium Neisseria gonorrhoeae, which causes gonorrhea. The complications related to it are proctitis, urethritis, conjunctivitis, reactive arthritis, epididymitis (only in men), cervicitis, and pelvic inflammatory disease (only in women), among others.

It’s important to note that chlamydia can be passed from mother to child during labor. As a result, this can cause neonatal conjunctivitis or neonatal pneumonia. Prenatal detection is key to avoiding complications in newborn babies.

Although it’s a bacterium that contains its own DNA, RNA, ribosomes and is capable of synthesizing nucleic acids and proteins, it depends on a host cell to survive. At the same time, its behavior within the organism emulates that of a virus and a parasite.

Chlamydia is caused by an infection with a bacterium that belongs to a very broad genus. We’ll now find out how it’s transmitted and who is most likely to get it.

Chlamydia risk factors

Causes of chlamydia include promiscuity
Being a sexually transmitted disease, promiscuity and the infrequent use of barrier methods are important risk factors.

Chlamydia is transmitted through direct contact with secretions, especially cervical mucus and semen (among others). It isn’t transmitted through physical contact or through fluids such as saliva. Sexual intercourse, whether vaginal or anal, is the main means of transmitting the bacteria. However, as we’ve pointed out, labor is also a channel of contagion.

Research has shown that young people aren’t very aware of how chlamydia is transmitted. When you combine this with the absence of symptoms, this partially explains the growing increase in cases, as some research indicates.

The United States Centers for Disease Control and Prevention (CDC) reminds us of the following risk factors:

  • Having unprotected sex: Condoms reduce the chances of contracting chlamydia by more than 90%, both in vaginal and anal sex. Since oral sex is also a channel of transmission, practicing it with an infected person encourages the transmission of the bacteria.
  • Having many sexual partners: The chances of getting chlamydia are higher in people whose sex lives involve different partners. These increase if protection isn’t used in these sexual encounters.
  • Being HIV positive: It’s estimated that up to 10% of patients diagnosed with HIV have chlamydia or gonorrhea.
  • History of having STDs or currently being infected with one: The physiological reactions that occur in the body can predispose a person to a contagion of this type.
  • Vaginal flora: In the case of women, the use of products during a vaginal douche can alter the flora that helps fight infections.
  • Suffering from cervical ectopia: It has been suggested that young women with cervical ectopia are more likely to develop chlamydial infections when compared to groups without this condition.

Importantly, this STD can develop regardless of sexual preference. Any type of anal, vaginal or oral sex that is performed without protection increases the chances of contracting the bacteria.

When should you go and see the doctor?

People who have multiple sexual partners should be screened at least once a year. If you find out that your partner (or someone else you have had intimate relations with) has chlamydia, then you should also get tested.

Should you should experience discharges in your genitals, pain when urinating, pain in the lower abdomen, or pain during sex, then consult a specialist to confirm the diagnosis. If you experience any of the symptoms we’ve mentioned in this article, then you can suppose that you too have contracted the bacteria.

Chlamydia can be cured based on treatment to attack the infection. The important thing here is to act in time in order to avoid complications, and so an early diagnosis is of great help.



  • Araya, V., Pezoa, K., Saavedra, M., & Aravena, J. (2019). Conocimiento y creencias sobre infección por Clamidia en población joven. Revisión narrativa. Revista chilena de obstetricia y ginecología. 2019; 84(5): 403-415.
  • Jones, J., Weiss, K., Mermin, J., Dietz, P., Rosenberg, E. S., Gift, T. L., … & Jenness, S. M. Proportion of incident HIV cases among men who have sex with men attributable to gonorrhea and chlamydia: a modeling analysis. Sexually transmitted diseases. 2019; 46(6): 357.
  • Lee, V., Foley, E., & Tobin, J. M. Relationship of cervical ectopy to chlamydia infection in young women. BMJ Sexual & Reproductive Health. 2006; 32(2): 104-106.
  • Piñeiro, L., Galán, J. C., & Vall-Mayans, M. Infecciones por Chlamydia trachomatis (incluye linfogranuloma venéreo) y Mycoplasma genitalium. Enfermedades infecciosas y microbiologia clínica. 2019; 37(8): 525-534.
  • Roca, B. Infecciones por clamidias. In Anales de medicina interna. 2007; 24 (6): 292-299.

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