What is Chlamydial Infection?

Chlamydial ("kla-MID-ee-uhl") infection is a curable sexually transmitted disease (STD), which is caused by a bacterium called Chlamydia trachomatis. You can get genital chlamydial infection during oral, vaginal, or anal sexual contact with an infected partner. It can cause serious problems in men and women as well as in newborn babies of infected mothers.

Chlamydial infection is one of the most widespread bacterial STDs in the United States. The U.S. Centers for Disease Control and Prevention (CDC) estimates that more than 4 million people are infected each year. Health economists estimate that chlamydial infections and the other problems they cause cost Americans more than $2 billion a year.

What Are the Symptoms of This STD?

Because chlamydial infection does not make most people sick, you can have it and not know it. Those who do have symptoms may have an abnormal discharge (mucus or pus) from the vagina or penis or pain while urinating. These early symptoms may be very mild. Symptoms usually appear within one to three weeks after being infected. Because the symptoms may be mild or not exist at all, you might not seek care and get treated.

The infection may move inside the body if it is not treated. There, it can cause pelvic inflammatory disease (PID) in women and epidydimitis in men, two very serious illnesses.

C. trachomatis can cause inflamed rectum and inflammation of the lining of the eye ("pink eye"). The bacteria also can infect the throat from oral sexual contact with an infected partner.

How Does the Doctor Diagnose Chlamydial Infection?

Chlamydial infection is easily confused with gonorrhea because the symptoms of both diseases are similar and the diseases can occur together, though rarely.

The most reliable ways to find out whether the infection is chlamydial are through laboratory tests. Usually, a doctor or other health care worker will send a sample of pus from the vagina or penis to a laboratory that will look for the bacteria.

The urine test does not require a pelvic exam or swabbing of the penis. Results from the urine test are available within 24 hours.

How is Chlamydial Infection Treated?

If you are infected with C. trachomatis, your doctor or other health care worker will probably give you a prescription for an antibiotic such as azithromycin (taken for one day only) or doxycycline (taken for seven days) to treat people with chlamydial infection. Or, you might get a prescription for another antibiotic such as erythromycin or ofloxacin.

Doctors may treat pregnant women with azithromycin or erythromycin, or sometimes, with amoxicillin. Penicillin, which doctors often use to treat some other STDs, won't cure chlamydial infections.

If you have chlamydial infection:

• Take all of the prescribed medicine, even after symptoms disappear.
• If the symptoms do not disappear within one to two weeks after finishing the medicine, go to your doctor or clinic again.
• It is very important to tell your sex partners that you have chlamydial infection so that they can be tested and treated.

What Can Happen if the Infection is Not Treated?

In women, untreated chlamydial infections can lead to PID. In men, untreated chlamydial infections may lead to pain or swelling in the scrotal area, which is a sign of inflammation of a part of the male reproductive system located near the testicles known as the epididymis. Left untreated, these complications can prevent people from having children.

Each year up to 1 million women in the United States develop PID, a serious infection of the reproductive organs. As many as half of all cases of PID may be due to chlamydial infection, and many of these don't have symptoms. PID can cause scarring of the fallopian tubes, which can block the tubes and prevent fertilization from taking place. Researchers estimate that 100,000 women each year become infertile because of PID.

In other cases, scarring may interfere with the passage of the fertilized egg to the uterus during pregnancy. When this happens, the egg may attach itself to the fallopian tube. This is called ectopic or tubal pregnancy. This very serious condition results in a miscarriage and can cause death of the mother.

Can Chlamydial Infection Affect a Newborn Baby?

A baby who is exposed to C. trachomatis in the birth canal during delivery may develop an eye infection or pneumonia. Symptoms of conjunctivitis or "pink eye," which include discharge and swollen eyelids, usually develop within the first 10 days of life.

Symptoms of pneumonia, including a cough that gets steadily worse and congestion, most often develop within three to six weeks of birth. Doctors can treat both conditions successfully with antibiotics. Because of these risks to the newborn, many doctors recommend that all pregnant women get tested for chlamydial infection.

How Can I Prevent Getting Chlamydial Infection?

You can reduce your chances of getting chlamydia or of giving it to your partner by using male latex condoms correctly every time you have sexual intercourse.

If you are infected but have no symptoms, you may pass the bacteria to your sex partners without knowing it. Therefore, any doctors recommend that anyone who has more than one sex partner, especially women under 25 years of age, be tested for chlamydial infection regularly, even if they don't have symptoms.

What Research is Going On?

Scientists are looking for better ways to diagnose, treat, and prevent chlamydial infections. NIAID-supported scientists recently completed sequencing the genome for C. trachomatis. The sequence represents an encyclopedia of information about the organism. This accomplishment will give scientists important information as they try to develop a safe and effective vaccine. Developing topical microbicides (preparations that can be inserted into the vagina to prevent infection) that are effective and easy for women to use is also a major research focus.