What is chlamydia?

Chlamydia is a common sexually transmitted disease (STD) caused by infection with Chlamydia trachomatis. It can cause cervicitis in women and urethritis and proctitis in both men and women. Chlamydial infections in women can lead to serious consequences including pelvic inflammatory disease (PID), tubal factor infertility, ectopic pregnancy, and chronic pelvic pain. Lymphogranuloma venereum (LGV), another type of STD caused by different serovars of the same bacterium, occurs commonly in the developing world, and has more recently emerged as a cause of outbreaks of proctitis among men who have sex with men (MSM) worldwide.

How common is chlamydia?

Chlamydia is the most frequently reported bacterial sexually transmitted infection in the United States. In 2010, 1.4 million cases of chlamydia were reported to the U.S.CDC from 50 states and the District of Columbia, but an estimated 2.86 million infections occur annually. A large number of cases are not reported because most people with chlamydia do not have symptoms and do not seek testing. Chlamydia is most common among young people. It is estimated that one in 15 sexually active females aged 14-19 years has chlamydia.

How do people get chlamydia?

People get chlamydia by having sex (anal, vaginal or oral) with someone who has the infection. Chlamydia can still be transmitted even if a man does not ejaculate. People who have had chlamydia and have been treated can get infected again if they have sex with an infected person.

Chlamydia can be spread from an infected woman to her baby during childbirth.

Who is at risk for chlamydia?

Any sexually active person can be infected with chlamydia. Anyone with genital symptoms such as discharge, burning during urination, unusual sores, or rash should refrain from having sex until they are able to see a health care provider about their symptoms.

Also, anyone with an oral, anal or vaginal sex partner who has been recently diagnosed with an STD should see a health care provider for evaluation.

Because chlamydia is usually asymptomatic, screening is necessary to identify most infections. Screening programs have been demonstrated to reduce rates of adverse sequelae in women. CDC recommends yearly chlamydia screening of all sexually active women age 25 or younger and older women with risk factors for chlamydial infections (e.g., women who have a new or more than one sex partner). Pregnant women should be screened during their first prenatal care visit. Pregnant women younger than 25 or at increased risk for chlamydia (e.g., women who have a new or more than one sex partner) should be screened again in their third trimester. Any woman who is sexually active should discuss her risk factors with a health care provider who can then determine if more frequent screening is necessary.

Routine screening is not recommended for men. However, the screening of sexually active young men should be considered in clinical settings with a high prevalence of chlamydia (e.g., adolescent clinics, correctional facilities, and STD clinics) when resources permit and do not hinder screening efforts in women.

Men who have sex with men (MSM) who have receptive anal sex should be screened for chlamydia each year. MSM who have multiple and/or anonymous sex partners should be screened more frequently (e.g., at three to six month intervals).

HIV-infected sexually active women who are age 25 or younger or have other risk factors, and all HIV-infected patients who report having receptive anal sex should be screened for chlamydia at their first HIV care visit and then at least annually. A patient’s health care provider might determine more frequent screening is necessary, based on the patient’s risk factors.

What are the symptoms?

Chlamydia is known as a “silent” infection because most infected people have no symptoms. If symptoms do occur, they may not appear until several weeks after exposure. Even when it causes no symptoms, chlamydia can damage a woman’s reproductive organs.

In women, the bacteria first infect the cervix (structure that connects the vagina or birth canal to the uterus or womb) and/or the urethra (urine canal). Some infected women have an abnormal vaginal discharge or a burning sensation when urinating. Untreated infections can spread upward to the uterus and fallopian tubes (tubes that carry fertilized eggs from the ovaries to the uterus), causing pelvic inflammatory disease (PID). PID can be silent, or can cause symptoms such as abdominal and pelvic pain. Even if PID causes no symptoms initially, it can lead to infertility (not being able to get pregnant) and other complications later on.

Some infected men have discharge from their penis or a burning sensation when urinating. Pain and swelling in one or both testicles (known as “epididymitis”) may occur, but is less common.

Chlamydia can infect the rectum in men and women, either through receptive anal sex, or possibly via spread from the cervix and vagina. While these infections often cause no symptoms, they can cause rectal pain, discharge, and/or bleeding (known as “proctitis”).

What kinds of complications can the infection cause?

The initial damage that chlamydia causes often goes unnoticed. However, chlamydial infections can lead to serious health problems.

In women, unt Untreated infection can spread upward to the uterus and fallopian tubes (tubes that carry fertilized eggs from the ovaries to the uterus), causing pelvic inflammatory disease (PID). PID can be silent, or can cause symptoms such as abdominal and pelvic pain. Both symptomatic and silent PID can cause permanent damage to a woman’s reproductive tract and lead to long-term pelvic pain, inability to get pregnant and potentially deadly ectopic pregnancy (pregnancy outside the uterus).

Complications are rare in men. Infection sometimes spreads to the tube that carries sperm from the testis, causing pain, fever, but, rarely, preventing a man from being able to father children.

How does chlamydia affect a pregnant woman and her baby?

In pregnant women, untreated chlamydia has been associated with pre-term delivery, and can spread to the newborn, causing an eye infection or pneumonia. Screening and treatment of chlamydia during pregnancy is the best way to prevent these complications. All pregnant women should be screened for chlamydia at their first prenatal visit.

How is chlamydia diagnosed?

There are laboratory tests to diagnose chlamydia. Specimens commonly used for testing include a cotton swab of the vagina (collected by the woman herself or her health care provider) or a urine sample.

How is chlamydia treated?

Penicillin is not effective against chlamydia.

Chlamydia can be easily treated and cured with antibiotics. HIV-positive persons with chlamydia should receive the same treatment as those who are HIV-negative.

Persons with chlamydia should abstain from having sex for seven days after single dose antibiotics, or until completion of a seven-day course of antibiotics, to prevent spreading the infection to partners.

Repeat infection with chlamydia is common. Persons whose sex partners have not been appropriately treated are at high risk for re-infection. Having multiple chlamydial infections increases a woman's risk of serious reproductive health complications, including pelvic inflammatory disease and ectopic pregnancy. Women and men with chlamydia should be retested about three months after treatment of an initial infection, regardless of whether they believe that their sex partners were successfully treated.

Infants infected with chlamydia may develop conjunctivitis (infection of the membrane lining the eyelids) and/or pneumonia. Chlamydial infection in infants can be treated with antibiotics.

What about partners?

If a person has been diagnosed and treated for chlamydia, he or she should tell all anal, vaginal or oral sex partners from the past two months so that they can see a health care provider and be treated. This will reduce the risk that the sex partners will develop serious complications from chlamydia and will reduce the person’s risk of becoming re-infected. A person with chlamydia and all of his or her sex partners must avoid having sex until they have completed their treatment for chlamydia (i.e., seven days after a single dose of antibiotics or until completion of a seven-day course of antibiotics) and until they no longer have symptoms.

To help get partners treated quickly, health care providers may give patients extra medicine or prescriptions to give to their sex partners. This is called expedited partner therapy or EPT. EPT is only available in some parts of the country, it is available in Illinois. Consult a health care provider to find out if it is available in a specific area. Sex partners should still be encouraged to see a health care provider, regardless of whether they receive EPT.

How can chlamydia be prevented?

Not having sex is the best protection against chlamydia and other STDs. Having sex with only one uninfected partner who only has sex with you is also safe. Latex male condoms, when used consistently and correctly, can reduce the risk of getting or giving chlamydia. The surest way to avoid chlamydia is to abstain from vaginal, anal and oral sex or to be in a long-term mutually monogamous relationship with a partner who has been tested and is known to be uninfected.

Where can I get more information?

Illinois Department of Public Health

HIV/STD Hotline 800-243-2437 (TTY 800-782-0423)

U.S. Centers for Disease Control and Prevention (CDC)
CDC-INFO Hotline (7am-7pm Mon.-Fri. Closed Holidays)

STD information and referrals to STD Clinics
800-CDC-INFO (800-232-4636)
TTY: 888-232-6348
In English, en Español

CDC National Prevention Information Network (NPIN)
P.O. Box 6003
Rockville, MD 20849-6003
888-282-7681 Fax

American Social Health Association (ASHA)
P. O. Box 13827
Research Triangle Park, NC 27709-3827

May 2013

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idph online home

Illinois Department of Public Health
535 West Jefferson Street
Springfield, Illinois 62761
Phone 217-782-4977
Fax 217-782-3987
TTY 800-547-0466
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