Chlamydia is the most frequently reported bacterial sexually transmitted infection in the United States. In 2012, 1,422,976 cases of chlamydia were reported to 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 1 in 15 sexually active females aged 14-19 years has Chlamydia.

People get chlamydia by having sex with someone who has the infection. “Having sex” means anal, vaginal, or oral sex. 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 also be spread from an infected woman to her baby during childbirth.

Any sexually active person can be infected with Chlamydia. It is a very common STI, especially among young people. It is estimated that 1 in 15 sexually active females aged 14-19 years has Chlamydia.

Sexually active young people are at high risk of acquiring chlamydia for a combination of behavioral and biological reasons. Men who have sex with men (MSM) are also at risk for chlamydial infection since chlamydia can be transmitted by oral or anal sex

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 also occur, but is less common.

Chlamydia can also 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”).

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

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 the reproductive tract and lead to long-term pelvic pain, inability to get pregnant, and potentially deadly ectopic pregnancy (pregnancy outside the uterus).

In pregnant patients, untreated chlamydia has been associated with pre-term delivery, and can spread to the newborn, causing an eye infection or pneumonia.

Complications are rare in men. Infection sometimes spreads to the tubes that carry sperm from the testis causing pain, fever, and sometimes prevents a man from being able to father children.

Untreated chlamydia may increase a person’s chances of acquiring or transmitting HIV – the virus that causes AIDS.

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

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

If a person has been diagnosed and treated for Chlamydia, they should tell all anal, vaginal, or oral sex partners from the past two months so that they can see a healthcare provider and be treated. This will reduce the risk that the sex partners will develop serious complications from chlamydia and will also reduce the person’s risk of becoming re-infected. A person with chlamydia, and all of their sex partners, should 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, healthcare 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. Consult a healthcare provider to find out if it is available in a specific area. Sex partners should still be encouraged to see a healthcare provider, regardless of whether they receive EPT.