Symptoms include a discharge from the penis or vagina and painful or more frequent urination.
If unnoticed or untreated in women, these infections can result in infertility, miscarriage, and an increased risk of a mislocated (ectopic) pregnancy.
DNA tests of a sample of the discharge or of urine can detect chlamydial infection.
Antibiotics can cure the infection, and sex partners should be treated at the same time.
(See also Overview of Sexually Transmitted Infections Overview of Sexually Transmitted Infections (STIs) Sexually transmitted (venereal) diseases are infections that are typically, but not exclusively, passed from person to person through sexual contact. Sexually transmitted infections may be caused... read more 
.)
Several bacteria, including Chlamydia trachomatis (chlamydiae), Ureaplasma, and Mycoplasma, cause similar diseases, all of which resemble the sexually transmitted infection (STI) gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, and throat or the membranes that cover... read more 
. Laboratories can identify chlamydiae but have difficulty identifying the other bacteria, so these are sometimes called nongonococcal infections.
Chlamydial infection is the most commonly reported STI. In the United States, over 1.8 million cases were reported in 2018. Because the infection frequently causes no symptoms, twice as many people than are reported to have chlamydial infection may actually be infected.
Chlamydial infection and gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, and throat or the membranes that cover... read more cause similar symptoms. Both can cause urethral infections (urethritis Urethritis Urethritis is infection of the urethra, the tube that carries urine from the bladder out of the body. Bacteria, including those that are sexually transmitted, are the most common cause of urethritis... read more ) in men and, in women, cervical infections (cervicitis Cervicitis Cervicitis is inflammation of the cervix (the lower, narrow part of the uterus that opens into the vagina). It may be caused by an infection or another condition. Cervicitis is often caused... read more ) that produce pus (see also Chlamydial Infections and Mycoplasmas Chlamydial Infections and Mycoplasmas ).
Sometimes people have gonorrhea and chlamydial infection at the same time.
Symptoms
In men, symptoms of chlamydial urethritis start 7 to 28 days after the infection is acquired during intercourse. Typically, men feel a mild burning sensation in their urethra during urination and may have a clear or cloudy discharge from the penis. The discharge is usually less thick than the discharge in gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, and throat or the membranes that cover... read more . The discharge may be small, and symptoms mild. However, early in the morning, the opening of the penis is often red and stuck together with dried secretions. Occasionally, the infection begins more dramatically—with a frequent urge to urinate, painful urination, and a discharge of pus from the urethra.
Many women with chlamydial cervicitis have few or no symptoms. But some have frequent urges to urinate, painful urination, and a discharge of yellow mucus and pus from the vagina. Sexual intercourse may be painful.
If the rectum is infected, people may have rectal pain or tenderness and a yellow discharge of pus and mucus from the rectum.
Chlamydial infection can also be spread during oral sex, causing infection of the throat. Chlamydial throat infection usually causes no symptoms.
Without treatment, symptoms lessen within 4 weeks in about two thirds of people. However, chlamydial infections can have serious long-term consequences for women, even when their symptoms are mild or absent. Thus, detecting the infection in women and treating them is important, even if symptoms are absent.
Complications
In women, complications from chlamydial infection include
Scarring of the fallopian tubes
Infection of the fallopian tubes (salpingitis)
Infection of the membrane that lines the pelvis and abdominal cavity (peritonitis)
Infection in the area around the liver
The infection may spread up the reproductive tract and may infect the tubes that connect the ovaries to the uterus (fallopian tubes). This infection, called salpingitis, causes severe lower abdominal pain. In some women, the infection spreads to the lining of the pelvis and abdominal cavity (peritoneum), causing peritonitis. Peritonitis causes more severe pain in the lower abdomen. These infections are considered pelvic inflammatory disease Pelvic Inflammatory Disease (PID) Pelvic inflammatory disease is an infection of the upper female reproductive organs (the cervix, uterus, fallopian tubes, and ovaries). Pelvic inflammatory disease is usually transmitted during... read more 
. Sometimes infection concentrates in the area around the liver, in the upper right part of the abdomen, causing pain, fever, and vomiting—called the Fitz-Hugh-Curtis syndrome.
Complications include chronic abdominal pain and scarring of the fallopian tubes. The scarring can cause infertility and mislocated (ectopic) pregnancies Ectopic Pregnancy Ectopic pregnancy is attachment (implantation) of a fertilized egg in an abnormal location, such as the fallopian tubes. In an ectopic pregnancy, the fetus cannot survive. When an ectopic pregnancy... read more .
In men, complications from chlamydial infection include
Infection of the epididymis
Narrowing (stricture) of the urethra
Chlamydial infections may cause infection of the epididymis (epididymitis Epididymitis and Epididymo-orchitis Epididymitis is inflammation of the epididymis (the coiled tube on top of the testis that provides the space and environment for sperm to mature), and epididymo-orchitis is inflammation of the... read more ). The epididymis is the coiled tube on top of each testis (see figure Pathway From the Penis to the Epididymis Pathway From the Penis to the Epididymis 
). This infection causes painful swelling of the scrotum on one or both sides. The infection may lead to narrowing of the urine passage through the penis (urethra) due to scarring.
Pathway From the Penis to the Epididymis
Occasionally in men, organisms spread up the urethra and travel through the tube that carries sperm from the testis (vas deferens) to infect the epididymis at the top of a testis.  |
In either sex, complications from chlamydial infection include
Infection of the membrane that covers the white of the eye (conjunctivitis)
Reactive arthritis
Chlamydial genital infections occasionally cause a joint inflammation called reactive arthritis Reactive Arthritis Reactive arthritis (previously called Reiter syndrome) is a spondyloarthritis causing inflammation of the joints and tendon attachments at the joints, often related to an infection. Joint pain... read more 
(previously called Reiter syndrome). Reactive arthritis typically affects only one or a few joints at once. The knees and other leg joints are affected most often. The inflammation seems to be an immune reaction to the genital infection rather than spread of the infection to the joints. Symptoms typically begin 1 to 3 weeks after the initial chlamydial infection. Reactive arthritis sometimes is associated with other problems, such as changes in the skin of the feet, problems with the eyes, and inflammation of the urethra.
In newborns, complications from chlamydial infection include
Conjunctivitis
Pneumonia
Newborns may be infected with Chlamydia during delivery if their mother has a chlamydial infection of the cervix. In newborns, the infection may result in pneumonia or conjunctivitis (neonatal conjunctivitis Conjunctivitis in Newborns Conjunctivitis is inflammation of the conjunctiva, the membrane that lines the eyelid and covers the white of the eye. Conjunctivitis is caused by bacteria, viruses, or a reaction to chemicals... read more 
).
Diagnosis
Usually tests on a sample of discharge from the cervix, penis, throat, or rectum or a sample of urine
Doctors suspect chlamydial, ureaplasmal, and mycoplasmal infections based on symptoms, such as a discharge from the penis or cervix.
In most cases, doctors diagnose chlamydial infections by doing tests that detect the bacteria’s unique genetic material (DNA). Usually, a sample of the discharge from the penis or cervix is used. Sometimes women are asked to use a swab to obtain a sample from their vagina. For some types of these tests, a urine sample can be used. If a urine sample can be used, people can avoid the discomfort of having a swab inserted into the penis or having a pelvic examination to obtain a sample.
If doctors suspect infection of the throat or rectum, samples from those sites may be tested.
Gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, and throat or the membranes that cover... read more , which is often also present, can be diagnosed using the same sample. Blood tests to check for human immunodeficiency virus (HIV) infection Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more 
and syphilis Syphilis Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. Syphilis can occur in three stages of symptoms, separated by periods of apparent good health. It... read more 
are usually also done.
Screening
Because chlamydial infection is so common and because many infected women have no symptoms, tests to screen for chlamydial infection and other STIs are recommended for certain sexually active women and men.
Women who are not pregnant (including women who have sex with women) are screened annually if they have characteristics that increase their risk of infection:
Sexually active and under age 25
A previous STI
Participation in risky sexual activities (such as having many sex partners, not using condoms regularly, or participating in sex work)
A partner who participates in risky sexual activities or has an STI
Pregnant women are screened during their initial prenatal visit. The following pregnant women are screened again during the 3rd trimester:
All who are under age 25
Those who are age 25 and older if their risk of infection is increased
If pregnant women have a chlamydial infection, they are treated. These women are tested again within 3 months.
Heterosexually active men are not routinely screened except if their risk of chlamydial infection is increased—for example, when they have several sex partners, when they are patients at an adolescent or STI clinic, or when they are admitted into a correctional facility.
Men who have sex with men are screened as follows:
If they are sexually active: At least once a year
If they are at increased risk (those with HIV infection, multiple sex partners, or a partner who has multiple partners): Every 3 to 6 months
These men are screened whether they use condoms or not. Tests are done using samples taken from the rectum, the urethra, or, if they engaged in oral sex, the throat.
Prevention
The following general measures can help prevent chlamydial infections (and other STIs):
Avoidance of unsafe sex practices, such as frequently changing sex partners or having sexual intercourse with prostitutes or with partners who have other sex partners
Prompt diagnosis and treatment of the infection (to prevent spread to other people)
Identification of the sexual contacts of infected people, followed by counseling or treatment of these contacts
Not having sex (anal, vaginal, or oral) is the most reliable way to prevent STIs but is often unrealistic.
Treatment
An antibiotic
Simultaneous treatment of sex partners
Chlamydial, ureaplasmal, and mycoplasmal infections are treated with one of the following antibiotics:
A single dose of the antibiotic azithromycin taken by mouth
Doxycycline, erythromycin, levofloxacin, or ofloxacin taken by mouth for 7 days
Pregnant women are treated with azithromycin.
If gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, and throat or the membranes that cover... read more is possible, an antibiotic such as ceftriaxone, injected into a muscle, is given at the same time to treat gonorrhea. Such treatment is needed because the symptoms of the two infections are similar and because many people have both infections at the same time.
Symptoms may persist or return for one of the following reasons:
Other infections that are also present may be causing the symptoms.
People may have become infected again.
The chlamydiae may be resistant to antibiotics.
In such cases, tests for chlamydial infection and gonorrhea are repeated, and sometimes tests for other infections are done. Then people are treated with azithromycin or, if azithromycin was used before and was ineffective, with moxifloxacin.
Sex partners should be treated simultaneously if possible. Infected people and their sex partners should abstain from sexual intercourse until they have been treated for at least 1 week.
The risk of another chlamydial infection or another STI within 3 to 4 months is high enough that people should be tested again at that time.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
