Updated on:
February 16, 2022

Chlamydia is a sexually transmitted infection (STI) caused by the bacteria Chlamydia trachomatis. It is easily passed from person to person through sexual contact. The bacteria tend to target warm, moist areas (i.e., mucous membranes) and may infect the mouth, throat, penis, vagina, and/or rectum. It can also infect the eyes if contaminated fluid comes into contact with them.

Many people infected with chlamydia are asymptomatic, meaning they exhibit no symptoms at all. Those who do have symptoms typically experience them within 2-6 weeks of the initial infection.

If left untreated, chlamydia can lead to serious long-term health effects. Through STI screening, usually collecting a urine sample and swabs of the affected area(s), chlamydia can be effectively detected and easily treated with antibiotics.

The history of chlamydia

How has our understanding of Chlamydia evolved?

Chlamydia bacteria was first discovered in cultures from the eye of an experimentally infected orangutan by scientists Halberstaedter and von Prowazek in 1907. They were associates of a German doctor and researcher, Albert Neisser, who discovered the gonorrhea bacteria in the late nineteenth century.

It wasn't until the 1970's that Chlamydia became recognized as a sexually transmitted infection, and by the mid-1990s, infection rates began to rise more rapidly.

Today chlamydia is the most common STI globally, second only to the human papillomavirus (HPV). Fortunately, methods for screening and treating chlamydia are simple and highly effective at curing the infection.

How prevalent is chlamydia in at-risk groups?

In Canada, chlamydia is the most commonly reported sexually transmitted infection.  The average rate of reported chlamydia infection in 2018 was 363.2 per 100,000 people. Between 2009-2018, reported chlamydia infection rates in Canada increased by 40%, with 117,008 reported in 2018. Females represented 59.6% of those reported cases, although infection rates for men have been increasing faster, by almost 67.6% since 2009. This difference is mainly due to higher rates of infection among men who have sex with men.

The highest proportion of reported chlamydia cases is amongst young adults aged 15-29, representing 76% of reported cases in 2017. Although all age groups over 15 experienced an increase in reported chlamydia rates, the highest rate of chlamydia is amongst 20-24 year-olds.

Chlamydia can affect anyone; however, some populations contain a higher risk for chlamydia. Gay, bisexual, and other men who have sex with men experience higher rates of chlamydia.

Factors that can increase your risk of contracting chlamydia include:

  • Inconsistent condom use
  • Having a new sexual partner
  • Having multiple sexual partners
  • Having anonymous sexual partners
  • Being a male who has sex with other males
  • Being a sex worker or having sex with sex workers
  • Being a young adult
  • Drug use
  • Lower socioeconomic status
  • Experiencing violence and/or discrimination
  • Experiencing mental health issues
  • Having previously contracted chlamydia or other STIs

Chlamydia myths

You will know you have chlamydia because you'll show symptoms.

Most people infected with chlamydia may not show or experience any symptoms. The only way to know if you have chlamydia is to get an STI test.

You can’t transmit chlamydia once you start antibiotics.

While antibiotics are highly effective at curing chlamydia, your healthcare provider will let you know when it is safe again to resume sexual activity. This is often seven days after either (1) a single high-dose antibiotic treatment or (2)  you’ve completed an entire course of 7-day oral antibiotics.

I only need to be treated for chlamydia if I test positive.

Recent sexual contacts of persons who have tested positive may also be recommended for empiric (i.e. an educated guess of potential transmission) treatment at the same time that they are getting tested as the risk of infection is high and the test might be falsely negative as the infection is relatively new. 

Chlamydia will clear up on its own.

Chlamydia is a bacterial infection that will not resolve independently without treatment by a healthcare provider in the form of antibiotics. Even if chlamydia symptoms never appear or they go away, the bacteria can still be transmitted to others and cause you serious, long-term complications if not treated.

Once you've been cured of chlamydia, you can't get it again.

Chlamydia can be contracted again by someone who previously had it and has recovered from it. Transmission is possible anytime there is sexual contact with an infected individual, and reinfection is common.

How is chlamydia transmitted?

Transmission of chlamydia occurs when secretions (fluid) from infected mucous membranes (i.e. throat, vagina, rectum), or semen from a person with a urethral (penile) infection, comes into contact with the mucous membranes of a non-infected person. The highest-risk behaviours in transmitting Chlamydia are penis-to-vagina (vaginal) or penis-to-anus (anal) sex. Additionally:

  1. Performing oral sex on someone that is infected with chlamydia can transmit the infection to your throat and/or mouth.
  2. If your partner has chlamydia in their mouth and they perform oral sex on you, they can transfer the chlamydia infection to your genitals or rectum.
  3. Sharing of sex toys
  4. Performing hand jobs or finger stimulation of the vagina or anus if infected fluids come into contact with the hand can transmit the chlamydia bacteria to mucous membranes the hand then comes into contact with (i.e. genitals, mouth/throat, eyes, rectum).
  5. Pregnant parents with chlamydia can also transmit the bacteria to their newborns during birth.

How to protect yourself from chlamydia transmission

Preventing chlamydia along with many other STIs can include a multitude of methods, including:

  • Correct and consistent condom use for penetrative sex and dental dams, and condoms for oral sex.
  • Practicing ideal hygiene before and after sexual activity, including:
  • Washing your body and genitals before and after sexual activity
  • Using antibacterial mouthwash after oral sex
  • Avoiding flossing your teeth within thirty minutes of giving oral sex
  • Speaking to your sexual partners about their STI and testing history.
  • Avoiding having sexual contact if you or your sexual partner notices any unusual discharge, pain or burning (especially when urinating), or discomfort in the genital or anal region.
  • Getting tested (and treated) for STIs regularly.

If you test positive for chlamydia (or other STIs), treat it as soon as possible and notify your sexual partners so they can get tested and treated to prevent future re-infection. Abstain from sexual contact until you're re-tested and the chlamydia is gone.

Is chlamydia treatable & curable?

Yes! The current first-line treatment to cure Chlamydia involves either macrolide or tetracycline antibiotics. Typically this consists of receiving either a single high-dose of antibiotic azithromycin or completing an entire seven-day course of antibiotics like doxycycline, usually taken twice daily.

If you cannot take those antibiotics due to allergies or another reason, your healthcare provider may prescribe alternative quinolone antibiotics taken for seven days like Levofloxacin.

If symptoms remain after initial treatment, follow up with your healthcare provider as you may require additional treatment or a different antibiotic.

Are there any current studies being performed to improve available medicine/treatments?

Currently, there are studies underway to find a vaccine that would prevent chlamydia transmission.

Reviewed by:
Dr. Caley Shukalek

Caley is passionate about evidence-based, patient-centred care, including telemedicine that can provide high quality care from wherever a patient may choose.

He helped create Alberta's PrEP guidelines and works as a specialist in General Internal Medicine with additional training in sexual health, including HIV and sexually transmitted infections.

He holds an Masters of Public Health from Johns Hopkins University, an MD from the University of Calgary and an MSc from the University of Alberta.