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  • Definition

    chlamydia is a sexually transmitted disease (STD) caused by bacteria that may cause pelvic infection and atypical pneumonia.


    Infections due to chlamydia ("klamid-ee-uh") are the most common bacterial (STDs) in the U.S. today, with an estimated 4 million new cases occurring each year.

    Chlamydial pelvic infections are caused by a bacterium, Chlamydia trachomatis. Among adults, these pelvic infections are transmitted during vaginal or anal sexual contact with an infected partner.

    A mother may also pass the infection to her newborn during delivery.

    A silent chlamydial infection of the cervix inflicts minimal damage, but all too often the organisms travel upward into the uterus, where they infect the endometrium.

    When chlamydia ascends further, to the Fallopian tubes and ovaries, it produces a condition known as pelvic inflammatory disease, which is also a common complication of gonorrhea. Chlamydial infections are easily confused with gonorrhea because the symptoms of both diseases are similar, and they often occur together.

    Pelvic inflammatory disease (PID) has emerged as a major cause of infertility and ectopic pregnancy among women of childbearing age.

    A particular strain of chlamydia causes an uncommon STD called lymphogranuloma venereum (LGV), which is characterized by swelling and inflammation of the lymph nodes in the groin. Other complications may follow if LGV is not treated at this stage.

    Other species, Chlamydia pneumoniae and Chlamydia psittaci, cause pneumonia and pneumonitis. Chlamydia bacteria have also been found in the throat.

    Chlamydial infection can also cause proctitis (inflammation of the rectum) and conjunctivitis (inflammation of the lining of the eye).


    Chlamydia is transmitted through unprotected sex. Barrier methods of contraception, especially condoms, thwart the transmission of chlamydia.


    The early symptoms of chlamydial infection are usually mild, for this reason it has sometimes been called "the silent STD."

    If symptoms occur, they usually appear within 1 to 3 weeks after exposure. Studies report that 10 to 20 percent of sexually active female teens harbor chlamydial infections. In up to 75 percent of cases, the infection is clinically inapparent. As a result, the disease is often not diagnosed until complications develop.

    Symptoms of chlamydial infection in the cervix, urethra, or anus may include intermittent vaginal bleeding or discharge, pain on urination, or ill-defined abdominal discomfort.

    In men, chlamydial infections cause about 40 percent of the cases of nongonococcal urethritis (NGU), an inflammation of the urinary tract. The most common symptom of NGU is a discharge of mucus or pus from the penis. Some men also notice pain when urinating. Pain or swelling in the scrotal area may be signs of epididymitis, an inflammation of a part of the male reproductive system located near the testicles. Up to 50 percent of men have no symptoms.


    The diagnosis is often made clinically and by exclusion. In women, a pelvic exam and cervical and urethral swabs for chlamydia and gonorrhea are performed. In men, a urethral swab is taken. Negative cultures or screenings do not completely rule out infection.

    Patients who have had sexual contact with a person documented as infected with gonorrhea or chlamydia should be treated immediately after cultures are taken, before results are reported.

    New and highly accurate urine tests, that don't require a pelvic exam or urethral swab, are now available in many locations to screen both females and males for chlamydial infection. Ask you doctor or public health clinic personnel about these.


    There are several very safe, effective and inexpensive treatments for chlamydia. Antibiotics may include doxycycline, azithromycin, ofloxacin, or erythromycin. Antibiotics to eradicate both chlamydia and gonorrhea are usually given to high-risk populations since both types of bacteria commonly coexist.

    Up to 95 percent of people with chlamydia are effectively cured with one course of antibiotics. Without treatment, some women will develop pelvic inflammatory disease that may lead to to liver disease, or to chronic pelvic pain and possible sterilization. Men may develop painful swelling of the testicles, sexually acquired reactive arthritis or Reiter syndrome.

    Sexual partners of infected patients should also be treated.


    What causes chlamydial infection?

    How is the disease transmitted?

    What are the symptoms in men and women?

    How is chlamydia diagnosed?

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    How effective are antibiotics?

    How can chlamydia be prevented?

    All sexually active persons should consider being tested for Chlamydia in order to stop transmitting it and to decrease the likelihood of complications such as pelvic inflammatory disease. Latex condoms used consistently and correctly are an effective means for preventing disease (and pregnancy). Talk openly with your partner about STDs, HIV, and hepatitis B infection, and the use of contraception.