What Is Chlamydia?

Chlamydia is a family of contagious microorganisms. Specific species can infect various sites in the body, including the genitals, eyes, lymph nodes, and respiratory tract. In developed countries, chlamydia trachomatis most commonly appears as a sexually transmitted genital infection, marked by urethritis in men and cervical infection in women.

Diagnosis of genital chlamydia may be difficult, especially in women, because the infection is often asymptomatic. In women, untreated infection may involve the fallopian tubes (salpingitis), which causes a syndrome known as pelvic inflammatory disease (PID). PID increases the risk of scarring, which can cause sterility and/or an increased risk of ectopic (tubal) pregnancy. In men, untreated infection may lead to epididymitis. In underdeveloped countries, other subtypes of chlamydia cause infection of the eyes (trachoma), a leading cause of blindness.

Chlamydia pneumoniae is a common cause of mild pneumonia; it has also been proposed as a potential cause of coronary artery disease. Psittacosis—a type of pneumonia that occurs in individuals exposed to birds and poultry processing plants—is caused by chlamydia psittaci. These organisms are of a different subtype than those that cause genital infection.

Who Gets Chlamydia?

Chlamydia is the most common bacterial sexually transmitted disease (STD), affecting three to four million Americans annually. While it is most common among teenagers and young adults, anybody can get it: half of all sexually active people between 18 and 30 may be infected. Nearly 75% of all new cases occur in women under the age of 25.


  • Genital disease: painful or burning urination; possible redness and itching in and around the urethra.

  • Discharge from the penis or vagina

  • Painful swelling of the scrotum; inflamed, painful lymph nodes in the groin area.

  • Lower abdominal pain.

  • When the eyes are affected, inflammation of the lining of the eyelids and the membrane covering the whites of the eyes (conjunctivitis).

  • Chlamydia pneumonia: fever, chills, shortness of breath, cough.

  • In newborns, difficulty in breathing and a staccato cough, indicating a respiratory chlamydial infection.

  • Psittacosis pneumonia: high fever (103°F to 106°F).

Other symptoms range from those of a mild flu to those of severe pneumonia.

Note: Most infected women and 50% of infected men experience no symptoms.

Causes/Risk Factors

  • Chlamydial trachomatis infections may be transmitted by vaginal or anal intercourse and by oral-genital contact.

  • Infection of the cervix in pregnant women may cause eye and respiratory infections in newborns.

  • Touching the eyes with contaminated hands may transfer the infection to the eyes.

  • Women with chlamydia are 3 to 5 times more likely to become infected with HIV if they are exposed to the virus.

  • The presence of one STD is always a risk factor for another, including HIV infection.

What If You Do Nothing?

Chlamydia should be treated immediately; otherwise, it may become chronic and lead to extensive inflammation and scarring of the genital tract in both men and women. In women, untreated infections can lead to pelvic inflammatory disease (PID), which may result in ectopic pregnancy and infertility, even in women who never develop clinical PID.


  • A sample of urethral or cervical discharge is taken.

  • Traces of chlamydia DNA can be detected in the urine using a new test.

  • Persons at risk—especially those under age 25 who are sexually active—should be screened every six to 12 months, whether or not symptoms are present.

  • Because infection may be asymptomatic, people with multiple sex partners should be tested annually, even if they feel fine.

Note: Anyone diagnosed with chlamydia should inform his or her sexual partners, who can then be treated as well.


Since symptoms seldom occur, testing is the only way to diagnose it with certainty. The good news is that chlamydia is also easy to detect and treat. Unlike herpes or AIDS (both viral in origin), chlamydia can be cured with antibiotics.

Antibiotics, such as azithromycin or doxycycline, will be prescribed and should be taken for the full term. Antibiotics will be administered to both sexual partners for genital chlamydia. Only one partner may exhibit symptoms, but both must be treated.

Erythromycin is the preferred treatment for pregnant women, nursing mothers, infants, children, and adults unable to tolerate tetracycline.


  • Avoid intimate contact with infected people until the infection is cured.

  • A monogamous sexual relationship with an uninfected partner or complete abstinence will protect against genital infection; otherwise, use condoms, other barrier methods, and spermicides to help reduce risk.

  • To prevent psittacosis, make sure that any imported or exotic pet bird has been quarantined for 30 days, and that birds of the parrot family have been treated with necessary antibiotics, before buying them.

Note: Oral contraceptives do not protect against STDs and may even increase the risk for chlamydia.

When To Call Your Doctor

Make an appointment with a doctor if you or your partner experience symptoms of genital chlamydia, if your inner eyelids become inflamed, or if you develop a high fever (over 102°F).

Robert Hurd, M.D., American Board of Internal Medicine and Professor of Endocrinology and Health Care Ethics, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network.