The Facts

Chlamydia is the most commonly reported bacterial sexually transmitted infection (STI) in North America, affecting both men and women, although women report the disease more often than men.

The infection is named after the bacterium that causes it, Chlamydia trachomatis. Most women and many men who are infected with the bacteria have no symptoms and therefore don't know they have chlamydia.

Chlamydia is easily treated, but it can sometimes lead to serious complications if it isn't caught early enough. It is estimated that up to 40% of untreated women will develop pelvic inflammatory disease (PID), which can be very painful. The risk of preterm delivery, ectopic pregnancy, or infertility also increases with an untreated chlamydia infection.


Chlamydia is spread during sexual contact and is highly infectious. It can be transmitted through vaginal, anal, or oral sex.

Newborn babies can get infected if their mothers have chlamydia. Nearly two-thirds of infants born vaginally (i.e., not by caesarean) to infected mothers will contract chlamydia during delivery. In newborns, chlamydia infections appear as eye problems or respiratory problems rather than the typical genital infections seen in adults.

Symptoms and Complications

People with chlamydia don't always have symptoms. About 80% of women and 50% of men won't show signs of infection. If symptoms start, they will show up within 1 to 3 weeks after exposure.

In men, chlamydia usually starts in the urethra. Symptoms often come and go, or might only be noticed during the first urination of the day. These include:

  • painful burning on urination
  • redness, swelling, burning, itching around the opening of the penis
  • discharge from the penis, usually milky-white, grey, or yellow in colour
  • scrotal pain
  • Reiter's syndrome, a type of arthritis that can damage the joints and eyes
  • inflammation of the coiled tube (epididymis) at the back of the testicle that stores and carries sperm. this is called epididymitis
  • prostatitis, an inflammation of the prostate
  • infertility, if the infection spreads from the urethra to the testicles

Chlamydia can cause a number of complications in both men and women, including:

  • conjunctivitis (pinkeye)
  • pharyngitis (sore throat)
  • genital lymphogranuloma, which produces genital ulcers and swollen glands
  • Reiter’s syndrome, a type of reactive arthritis

In women, chlamydia usually begins on the cervix. While symptoms are rare in women, they can include:

  • a yellowish vaginal discharge that might have a foul odour
  • painful burning during urination
  • bleeding between periods and after intercourse
  • pain during intercourse
  • pain in the lower abdomen

Women can also develop a number of serious complications from a chlamydia infection. If left untreated, it can cause:

  • Reiter’s syndrome, a type of reactive arthritis
  • pelvic inflammatory disease (PID), a serious condition that can permanently damage the fallopian tubes, uterus, and ovaries (this can cause infertility and chronic pain)
  • inflammation of the liver resulting in pain on the right side

In both women and men, chlamydia can infect the rectum. This causes:

  • rectal itching and bleeding
  • pain during defecation
  • mucus-like discharge

If the eyes are infected by chlamydia (conjunctivitis), symptoms are:

  • redness, itching, and discharge from the eyes
  • swollen eyelids

In infants with chlamydia, eye infections occur in about 20% to 50% of babies born to infected mothers, and the infection usually occurs within 2 weeks of delivery. If the infection isn't treated in time, it can lead to scarring of the cornea and permanent damage to vision. About 5% to 30% of babies born to infected mothers will get pneumonia, usually within 2 to 12 weeks after delivery. The chlamydial pneumonia can cause anything from mild symptoms to breathing problems that include a repetitive cough.

Making the Diagnosis

A doctor may use a cotton swab to collect bacteria samples from the cervix, rectum, or urethra. A first morning urine sample may also be taken. These may be sent to a lab and checked for the presence of chlamydia.

Since this infection might not have symptoms, your sexual partner(s) could also be infected and should be seen by a doctor in order to also be tested.

Treatment and Prevention

Chlamydia can be cured easily and quickly, often with a single dose of oral medication (pills). Despite the ease of treatment, thousands of people suffer serious complications each year such as infertility and chronic pain either because they had no symptoms or failed to recognize them until it was too late. Don't wait for symptoms to develop – have routine check-ups. Be aware that the risk of acquiring chlamydia increases with the number of sexual partners.

Since chlamydia infection can occur without symptoms, it's possible to unknowingly transmit this infection to others, or to get it from someone who doesn't know they have it. Women are more likely to be unaware they have chlamydia. Condoms help decrease the chance of transmission and should be used from the beginning to the end of sex.

Chlamydia in men, women, and babies is treated with various antibiotics. The exact choice depends on the person and the extent of infection.

Even if symptoms aren't obvious, or if they disappear quickly, you should finish any course of antibiotics for the full length of time prescribed. If symptoms don't go away within 1 to 2 weeks of completing treatment, see your doctor again. 3 to 4 weeks following the end of treatment, your doctor may want to see you again to make sure the infection is cured even if you are feeling well.

While undergoing treatment, and for at least 1 week after your last dose, you should avoid having sex.

At birth, infants are given an antibiotic ointment to prevent gonococcal eye infections. However, this antibiotic is not effective in preventing chlamydial eye infections, which are treated with oral antibiotics.