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Chlamydia is one of the most common sexually transmitted diseases (STDs). Symptoms can be subtle but can include abnormal vaginal discharge in women and painful urination in men. It can be prevented with safe sex practices and treated with antibiotics.
What is chlamydia infection?
Chlamydia trachomatis is a type of bacteria best known for causing the sexually transmitted infection known simply as chlamydia. It is among the most common sexually transmitted diseases (STDs), with more than a million cases reported each year in the U.S. alone.
However, the symptoms can be mild or even unnoticed, particularly in women, making screening for STDs particularly important for anyone who is sexually active. Some symptoms include abnormal vaginal discharge in women and pain with urination in men.
For the purposes of this article, we'll focus mainly on the STD that's most famously associated with chlamydia infection which can be prevented with safe sex practices and readily treated with antibiotics.
You should visit a physician to confirm the diagnosis where an antibiotic will be prescribed.
Symptoms of chlamydia infection
In developing countries, chlamydia infection of the eyes (known as trachoma) is among the leading preventable causes of blindness. Two less famous but closely related bacteria, Chlamydia pneumoniae and Chlamydia psittaci, are causes of the lung infections pneumonia and psittacosis respectively.
Regarding the STD, this form of chlamydia can also cause serious complications including infertility and even potentially fatal ectopic implantation of future pregnancies.
The symptoms of chlamydia vary somewhat between men and women. Generally speaking, men have more obvious symptoms but fewer long-term dangers. In either group, chlamydia can also infect the throat or rectum. In newborns of untreated mothers, infection during childbirth is more likely to involve the eyes or lungs. Adults can also be infected in these locations, though it is far less common.
In women, chlamydia typically infects the cervix (which separates the vagina from the uterus) and can spread to the uterus and fallopian tubes causing pelvic inflammatory disease (PID). Symptoms experienced by women may include the following.
- No symptoms: This is experienced by the majority of women, with some studies finding more than 85 percent of infected women were entirely asymptomatic.
- Abnormal vaginal discharge and/or bleeding: These are the main symptoms of cervicitis, or infection of the cervix, which is the most common site of chlamydia infection in women.
- Lower abdominal pain and fever: These may be signs of a more dangerous condition known as pelvic inflammatory disease (PID), which refers to bacterial cervicitis (typically caused by chlamydia or gonorrhea) that has spread to the uterus and fallopian tubes. PID is a particularly important complication of untreated chlamydia infection because it can cause potentially fatal pregnancy complications or infertility.
In men, chlamydia most commonly infects the urethra (which carries urine and semen through the penis) and can spread to other parts of the urogenital tract such as the prostate. Symptoms experienced by men may include the following.
- Painful urination (dysuria): This is relatively uncommon in women but it is among the most frequent symptoms of chlamydia infection in men. It is a sign of urethritis or inflammation of the tube which carries urine out of the body.
- Abnormal penile discharge: This is another classic symptom of chlamydia infection in men. The discharge may be clear or milky, classically contrasted with the thicker white discharge seen in gonorrhea infection.
- Painful ejaculation, pelvic pain or testicular pain: These are often signs that chlamydia has spread to deeper parts of the male genitourinary tract such as the prostate.
- Rectal pain: This can be a sign of proctitis or infection spread via anal intercourse. While it has been reported in women, it is most common in men who have sex with men.
Symptoms that can occur in anyone with chlamydia include the following.
- Sore throat: Pharyngitis is not a particularly common manifestation of chlamydia infection but can be seen as a result of oral sex with an infected partner.
- Painful lymph nodes in the groin: This is the main manifestation of a form of chlamydia infection known as lymphogranuloma venereum. However, this disease is unique to certain subspecies of chlamydia (serovars L1-L3) which are primarily found in Africa, Asia and the Caribbean.
- Pneumonia: This is caused by Chlamydia trachomatis and is rare in adults but is a common manifestation of chlamydia infection transmitted to newborns during childbirth .
- Eye infection: Chlamydia conjunctivitis is rare in the developed world but remains a significant risk to newborns worldwide. Chronic infection, known as trachoma, is a leading cause of preventable blindness.
- Joint pain: This is not caused by chlamydia infection itself, but by an autoimmune condition known as reactive arthritis which can develop following the infection. While reactive arthritis can occur in men or women, it typically follows the urethritis which is more common in men.
Causes of chlamydia infection
Chlamydia is most commonly transmitted through sexual activity; however, the main non-sexual cause of chlamydia in newborns is via childbirth.
Chlamydia is caused by infection with the bacteria Chlamydia trachomatis. Specifically, the common STD is caused by the subspecies serovars D through K, though other serovars can also cause important sexually transmitted infections. Most infections are spread through sexual contact, specifically unsafe sexual practices with an infected partner. This typically refers to penetrative vaginal sex but can also include oral or anal intercourse.
In addition to the genitals, other areas can become infected by chlamydia as a result of unsafe sexual contact. Throat infection (pharyngitis) is relatively uncommon and occurs mainly as a result of oral sex with an infected person. Rectal infection occurs mainly due to anal intercourse among men who have sex with men, though it is less likely to be symptomatic than other forms of infection.
Childbirth is the most common cause of non-sexual transmission of chlamydia. Unlike sexual transmission, transmission from an infected mother to her newborn most commonly manifests as pneumonia or eye infections (conjunctivitis or trachoma). Though most women with chlamydia do not pass the disease to their children, the severe consequences of this preventable infection underscore the importance of prenatal screening and appropriate newborn medical care.
Treatment options and prevention for chlamydia infection
Antibiotics and other treatments
Once diagnosed, chlamydia infection is usually fairly simple to treat.
- A single dose of oral antibiotics: Often a single, oral dose of the antibiotic azithromycin is sufficient to clear an uncomplicated infection.
- Longer courses of antibiotics: Alternative regimens involving longer courses of oral antibiotics are needed for those who cannot take azithromycin or who have more complicated forms of chlamydia infection. Since antibiotic resistance has been seen, you'll want to get tested again several weeks after treatment to ensure that the infection was fully cleared.
- Avoiding sexual activity: It is also important to avoid sexual activity after starting treatment, typically for one week or as advised by your physician.
- Alerting sexual partners: It is important to alert any sexual partners that they need to be tested and possibly treated. This can also be a difficult conversation, and your physician's office or local health department may be able to assist with anonymously alerting your sexual partner(s).
While the only certain way to avoid any STD is abstinence from sexual contact, that is rarely an effective long-term strategy. Widespread condom use is the best method for preventing the spread of STDs such as chlamydia.
The other important step in preventing chlamydia infection is early detection and treatment. Particularly given the high rates of asymptomatic infection, there is a significant risk of chlamydia and other STDs being spread by people who don't even know they are infected. That is why testing is recommended for anyone at high risk of exposure, such as young adults with multiple sexual partners. That's also why it is particularly important to be open and honest with your physician about private matters such as sexual practices.
When to seek further consultation for chlamydia infection
If you are concerned about STDs/STIs
Anyone concerned about sexually transmitted infections would be well-advised to seek professional medical care. Many STDs, including chlamydia, are easily treatable once they are identified but can become very dangerous if left untreated. Testing is also important due to the high risk of co-infection with other STDs, meaning exposure to one often involves concurrent exposure to others.
If you believe you need STD/STI screening
In general, STD screening is recommended in all sexually active adults who are at risk of exposure, such as those who do not use condoms consistently or those with multiple sexual partners. Due to the chance of asymptomatic infection and the risks associated with untreated STDs, screening is also recommended for all sexually active young women, regardless of symptoms or safe sexual practices. Women with a history of prior STDs should also let their physician know, particularly their obstetrician or gynecologist, as complications from an insufficiently treated disease can have long-term health implications. Thankfully, chlamydia infection is usually easy to cure with no lasting complications, but only if it is identified and treated appropriately.
Questions your doctor may ask to determine chlamydia infection
- Do you feel pain when you have sexual intercourse?
- When was your last menstrual period?
- When was the last time you had sex?
- Have you had any changes in your weight?
- Do you use birth control besides condoms?
Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.
Dr. Kelly is a graduate of the University of Pennsylvania Perelman School of Medicine, specializing in internal medicine and bioethics. He received his undergraduate degree from Emory University with a BA in Spanish. Dr. Kelly has formal training in medical interpretation and translation, along with several years of professional experience in medical communication and editing work for publication.
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- Chlamydia infections. U.S. National Library of Medicine: MedlinePlus. Updated May 31, 2018. MedlinePlus Link
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- Mishori R, McClaskey E, Winklerprins I. Chlamydia Trachomatis infections: Screening, diagnosis, and management. Am Fam Physician. 2012;86(12):1127-1132. AAFP Link