Chlamydia 101
Symptoms, testing & diagnosis, risk factors, treatment
What is chlamydia?
Chlamydia is an infection caused by the chlamydia trachomatis bacteria. It spreads primarily through vaginal, anal or oral sex with someone who is infected. It is the most commonly reported sexually transmitted infection in Canada, but it is sometimes called the “silent” infection because the majority of people who are infected do not have any symptoms and are unaware of their condition. If left untreated, chlamydia can cause serious health problems and lead to infertility. The only way to find out if you have it is to be tested. It can be diagnosed via swabbing or a urine sample and is treated with antibiotics.
How common is chlamydia?
Chlamydia is the most commonly reported bacterial STI in Canada and worldwide. Rates in Canada have been steadily rising since 1997[i], with the number of reported cases jumping from 87,283 in 2009 to 117,008 in 2018[ii] — an average increase of about 5 per cent per year.
More than three-quarters of chlamydia cases reported in Canada in 2018 were in patients aged under 30. It disproportionately affects sexually active youth and young adults.
The number of chlamydia cases far surpasses other common STIs in Canada, with 30,874 cases of gonorrhea reported in 2018, and 6,281 cases of infectious syphilis.
It is estimated that more than half of those infected with chlamydia are asymptomatic, which means the real number of infections is much higher than reported. It also means many infected individuals are contributing to the spread of infection without being aware of their condition.
Chlamydia is a different sexually transmitted infection to lymphogranuloma venereum (LGV), which is caused by variations of the bacteria that cause chlamydia. LGV infections are more invasive, with different symptoms[iii].
How can you get chlamydia?
Chlamydia is a bacterial infection that is usually transmitted through vaginal, anal and oral sex, or through contact with infected genital fluids. It can also be passed from mother to child during childbirth.
Despite numerous scare stories to the contrary, chlamydia cannot be spread by sitting on toilet seats, swimming in a pool or sharing baths, towels or cutlery. In addition to being transmitted through sex, chlamydia can also be spread via genital-to-genital contact, sharing sex toys that are not washed and through infected vaginal fluid or semen getting into your eye.
Those who have been treated for chlamydia and recover can get the infection again if they have sex with a person who has chlamydia.
What are the symptoms of chlamydia?
Although many people infected with chlamydia don’t have any symptoms, common symptoms include:
Vaginal discharge, or a discharge from the penis
A burning sensation when urinating
Pain in the lower abdomen, or during sex, as well as vaginal bleeding between periods or after sex (women)
Burning or itching at the opening of the penis and pain or swelling in the testicles (men)
Anal infections can include rectal bleeding, pain and discharge
Eye infections can occur due to contact with infected genitals
Symptoms generally appear two to six weeks after infection, but they can sometimes take longer to appear.
Chlamydia is most common in sexually active young people, especially women aged 15 to 24 in Canada.
If left untreated, it can lead to pelvic inflammatory disease (PID) in up to 40 per cent of infected women. Effects include abdominal pain, fever, abscesses, and pelvic pain. Some women can also suffer scarring to the fallopian tubes, which can cause infertility and an increased risk of life-threatening ectopic or tubal pregnancies.[iv]
Cases of Reiter’s Syndrome, which causes inflammation and swelling of the joints, have been recorded but are rare.
In pregnant women who have chlamydia, there is an increased risk that the baby will be born prematurely or develop eye infections or pneumonia.
In addition, chlamydia has been found to increase the infectiousness of and susceptibility to human immunodeficiency virus (HIV).[v]
In men, chlamydia left untreated can lead to pain and swelling in the testicles, known as epididymitis. Men who do not receive treatment for chlamydia can develop scarring of the urethra, which makes urinating difficult. It can also lead to infertility.
There have been some reports of men developing Reiter’s Syndrome, which causes inflammation and swelling of the joints, but it is rare.
Chlamydia has also been found to increase the infectiousness of and susceptibility to human immunodeficiency virus (HIV) in men and women.
How is chlamydia diagnosed?
A urine sample is normally required to test for chlamydia. In women, a sample is often taken from the cervix (not the same as a regular Pap exam). In men, a sample of discharge from the urethra may be taken for testing. The throat or rectum may also be tested for infection.
Testing is available free of charge in Canada via your family doctor or other clinics. Low-cost mobile testing options are also becoming increasingly popular for the privacy and convenience they offer.
How can you prevent chlamydia?
Chlamydia is extremely common but practicing safe sex can help reduce the risk of getting chlamydia and other sexually transmitted infections. That includes consistently and correctly using a condom and other barriers. The only way to completely avoid it is to avoid having vaginal, anal or oral sex, or to be in a monogamous relationship in which both partners have tested negative.
If you suspect you have chlamydia or are diagnosed, it’s important to tell your partners that they could have an infection.
Those at greatest risk of contracting chlamydia in Canada include sexually active youth and young people, especially women aged 15-24. The risk increases for those engaging in unprotected sex with different partners. Regular testing is recommended.
How can you treat chlamydia?
Chlamydia can be easily treated with antibiotics. However, it’s very important to complete your course of medication, even if your symptoms subside. Those infected with chlamydia can resume sexual activities only when directed to do so by their healthcare provider.
There isn’t currently a vaccine for chlamydia but there have been some promising results from clinical trials[vi]. A vaccine could have a major impact on public health worldwide, given the high rates of chlamydia across the world.
Chlamydia is a major cause of infertility worldwide, as noted in the World Health Organization’s global health sector strategy on sexually transmitted infections[vii]. It cites the development of point-of-care testing as a critical step to combating chlamydia infections.
In 2019, Canada released a five-year action plan for combating sexually transmitted and blood-borne infections including chlamydia[viii]. Increasing access to testing is one of seven priorities that underpin the plan.
[i] Choudhri Y, Miller J, Sandhu J, Leon A, Aho J, “Chlamydia in Canada, 2010-2015,” Can Commun Dis Rep, vol. 44, no. 2, pp. 49-54, 2018.
[ii] Overall and sex-specific rates of reported chlamydia cases in Canada, 2009-2018: Report on sexually transmitted infections in Canada, 2018 – Canada.ca
[iii] Public Health Agency of Canada, “Chlamydia and LGV: Key information and resources,” 2020: Chlamydia and LGV guide: Key information and resources – Canada.ca
[iv] Park, ST “Clinical characteristics of genital chlamydia infection in pelvic inflammatory disease” BMC Womens Health 2017 Jan 13;17(1):5 www.pubmed.ncbi.nlm.nih.gov/28086838/
[v] Galvin SR, Cohen MS. The role of sexually transmitted diseases in HIV transmission. Nat Rev Microbiol 2004 Jan;2(1):33-42. The role of sexually transmitted diseases in HIV transmission | Nature Reviews Microbiology
[vi]Abraham S, et al. Safety and immunogenicity of the chlamydia vaccine candidate CTH522 adjuvanted with CAF01 liposomes or aluminium hydroxide: a first-in-human, randomised, double-blind, placebo-controlled, phase 1 trial. The Lancet: 019 Oct;19(10):1091-1100: www.thelancet.com/journals/laninf/article/PIIS1473-3099(19)30279-8/fulltext
[vii] World Health Organization, “Global health sector strategy on sexually transmitted infections, 2016-2021,” WHO, 2016. www.apps.who.int/iris/bitstream/handle/10665/246296/WHO-RHR-16.09-eng.pdf;sequence=1
[viii] Public Health Agency of Canada, “Accelerating our response: Government of Canada five-year action plan on sexually transmitted and blood-borne infections,” Ottawa, 2019. www.canada.ca/en/public-health/services/reports-publications/accelerating-our-response-five-year-action-plan-sexually-transmitted-blood-borne-infections.html#a2