Chiamydial Infections

Chlamydial (kla-MIH-dee-ul) infection can take various forms and can affect the urinary and genital systems of the body, as well as the eyes and lungs. One of its most common forms is a sexually transmitted disease (STD), which usually is passed from one person to another through unprotected sexual intercourse.


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Chiamydia pneumoniae

Chiamydia psittaci

Chiamydia trachomatis



Pelvic Inflammatory disease (PID)


Sexually transmitted disease Venereal disease

What Are Chiamydial Infections?

There are different types of chlamydia bacteria. Chlamydia trachomatis (kla-MIH-dee-uh truh-KO-mah-tis) is the bacterium that causes genital (and sometimes throat) infections. People with this form of chlamydial infection might not know they have the disease, because symptoms of infection often do not appear right away. In both men and women, long-term complications can result from an untreated infection. The penis, vagina, cervix * , anus, or urethra * can become infected. Babies born to mothers with chlamydial infection may develop a type of conjunctivitis * shortly after birth. A different type of Chlamydia trachomatis also causes the most common infection-related form of blindness in the world.

Infection with Chlamydia pneumoniae (kla-MIH-dee-uh nu-MO-nye) can lead to pneumonia in humans and may be linked to an increased risk of heart disease. Humans also can contract Chlamydia psittaci (kla-MIHdee-uh sih-TAH-see) through contact with infected birds. This infection causes psittacosis (sih-tuh-KO-sis), or "parrot fever," a pneumonia-like illness. This form of chlamydial infection is the most rare, usually affecting only those people who work closely or live with birds.

Chlamydial infection is the most common STD in the United States. As many as 3 to 4 million new cases occur each year. Most people who contract chlamydia are younger than 25 years old. Of every 10 teenage girls tested for chlamydial infection, 1 girl has the infection.

* cervix (SIR-viks) is the lower, narrow end of the uterus that opens into the vagina.

* urethra (yoo-REE-thra) is the tube through which urine passes from the bladder to the outside of the body.

* conjunctivitis (kon-jung-tih-Wtis), often called 'pinkeye,' is an inflammation of the thin membrane that lines the inside of the eyelids and covers the surface of the eyeball. Conjunctivitis can be caused by viruses, bacteria, allergies, or chemical irritation.

How Do Chiamydial Infections Spread and What Are the Symptoms?

Spread by oral (by mouth), vaginal, and anal sexual intercourse, Chlamydia trachomatis is easily transmitted from person to person. Chlamydia also can pass from a woman to her baby during birth; infants born to infected mothers have about a 25 percent chance of becoming infected with conjunctivitis or pneumonia.

A microscopic image of a smear of material taken from the cervix of a woman infected with chlamydia shows the presence of the bacteria. Custom Medical Stock Photo, Inc.
A microscopic image of a smear of material taken from the cervix of a woman infected with chlamydia shows the presence of the bacteria.
Custom Medical Stock Photo, Inc.

The sexually-transmitted infection often is called "the silent epidemic," and up to half of men and three-fourths of women who have the disease do not know it, because symptoms can be mild or may not even be noticeable. Symptoms can take from 1 to 3 weeks to appear after a person becomes infected. Women may have a milky or yellowish discharge (mucus * or pus * ) from the vagina and experience pain while urinating or having sex. Fever, bleeding between periods, abdominal * pain, and the urge to urinate frequently are also signs of infection. Men may have a burning sensation when they urinate or a thin yellowish or milky discharge from the penis and swollen or tender testicles. Some men may not experience any symptoms. Chlamydia spread through oral contact with the genitals can cause an infection in the throat.

How Are the Diseases Diagnosed?

Specific testing for chlamydia is usually included when a person is screened for STDs. Tests for chlamydial infection and gonorrhea usually are done together, because the symptoms of these two sexually transmitted infections are similar. A doctor will ask about sexual history, collect a sample of urine for examination in a laboratory, and take cotton-swab samples from the cervix or the tip of the penis. If swelling or discharge is present, swabs also will be taken from the throat or anus. The material picked up by the swab is tested for the bacteria. Testing can take up to 3 days. Sometimes a quicker test that diagnoses chlamydial infection from a urine sample is used. Results from a urine sample usually can be obtained from a laboratory within a few hours. It is necessary for all sexual partners of a person who is diagnosed with chlamydial infection to be tested for the disease, even if they do not have symptoms.

What Is the Treatment for Chiamydial Infection?

Once a person is diagnosed with chlamydial infection, treatment with antibiotics begins. It is important for an infected person to finish all prescribed medication, even if symptoms disappear. If symptoms persist after taking all the medication, a follow-up visit to the doctor is necessary. Babies who contract chlamydia from their mothers also are treated with antibiotics.

* mucus (MYOO-kus) is a thick, slippery substance that lines the insides of many body parts.

* pus is a thick, creamy fluid, usually yellow or greenish in color, that forms at the site of an infection. Pus contains infection-fighting white cells and other substances.

* abdominal (ab-DAH-mih-nul) refers to the area of the body below the ribs and above the hips that contains the stomach, intestines, and other organs.

* uterus (YOO-teh-rus) is the muscular, pear-shaped internal organ in a woman where a baby develops until birth.

* fallopian (fah-LO-pee-uhn) tubes are the two slender tubes that connect the ovaries and the uterus in females. They carry the ova, or eggs, from the ovaries to the uterus.

* ovaries (O-vuh-reez) are the sexual glands from which ova, or eggs, are released in women.


If chlamydial infection is left untreated in women, it can move through a woman's reproductive organs and spread to the cervix, uterus * , fallopian tubes * , or ovaries * , causing pelvic inflammatory disease (PID). PID is a serious condition that can result in infertility (the inability to become pregnant). Each year, PID develops in up to a million women in the United States; half of these cases are the result of chlamydial infection. PID can scar and block the fallopian tubes and cause a woman to be at increased risk for an ectopic (ek-TAH-pik) pregnancy, in which the fertilized egg develops outside the uterus, usually within one of the fallopian tubes. Ectopic pregnancies are removed by emergency surgery to prevent the fallopian tube from rupturing and causing internal bleeding. Without emergency medical treatment, a ruptured ectopic pregnancy can result in severe bleeding that can lead to death. Women with a history of PID are 10 times more likely to have ectopic pregnancies than are other women. Research has shown that women who have chlamydia are up to five times more likely to become infected with the human immunodeficiency virus (HIV) * if they have unprotected sex with someone who has HIV infection.

In men, chlamydia can spread from the urethra to the testicles and may result in a condition called epididymitis * , which can lead to sterility (the inability to impregnate a woman). Men also can develop prostatitis (pros-tah-TY-tis), an inflammation of the prostate * , or Reiter syndrome (RYE-ter SIN-drome), a condition associated with arthritis * .


People who have chlamydial infection may pass the disease on to their sexual partners, even if they are not aware that they are infected. It is wise to approach any sexual relationship with a strong sense of responsibility. People who are sexually active are advised always to use a latex condom for all forms of sexual intercourse. Having several sexual partners puts a person at increased risk of all types of STDs. It is recommended that all men and women who are sexually active be screened regularly for STDs. The U.S. Centers for Disease Control and Prevention advises all sexually active women who have risk factors for chlamydial infection to be screened for STDs at least once a year, as part of a full gynecological exam. Women considered to be at risk are those who have new sex partners or who engage in sex with several partners and who do not use condoms during sex. Pregnant women are also screened, to prevent spreading the infection to their babies.

* HIV, or human immunodeficiency virus (HYOO-mun ih-myoo-no-dih-FIH-shen-see), is the virus that causes AIDS (acquired immunodeficiency syndrome).

* epididymitis (eh-pih-dih-duh-MY-tis) is a painful inflammation of the epididymis, a structure attached to the testicles.

* prostate (PRAH-state) is a male reproductive gland located near where the bladder joins the urethra. The prostate produces the fluid part of semen.

* arthritis (ar-THRY-tis) refers to any of several disorders characterized by inflammation of the joints.

See also
AIDS and HIV Infection
Congenital Infections
Sexually Transmitted Diseases



Planned Parenthood Federation of America, 810 Seventh Avenue, New York, NY 10019. Planned Parenthood posts information about sexually transmitted infections at its website.
Telephone 212-541-7800

U.S. National Institute of Allergy and Infectious Diseases (NIAID), Building 31, Room 7A-50, 31 Center Drive MSC 2520, Bethesda, MD 20892-2520. NIAID, part of the National Institutes of Health, posts fact sheets about many STDs, including chlamydial infections, at its website.

Telephone 301-496-5717

Website . KidsHealth is a website created by the medical experts of the Nemours Foundation and is devoted to issues of children's health. It contains articles on a variety of health topics, including chlamydial infections and other STDs.

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