Chlamydia
A common sexually transmitted infection often without symptoms.
Chlamydia is a sexually transmitted infection caused by the bacterium *Chlamydia trachomatis*, a pathogen that infects only humans. It is among the most common sexually transmitted infections globally, with an estimated 61 million new cases occurring worldwide in 2015. In the United States alone, approximately 1.4 million cases were reported in 2014. The infection disproportionately affects young people aged 15 to 25 and is more frequently diagnosed in women than in men. The term "chlamydia" derives from the Greek word for "cloak," reflecting the often-hidden nature of the disease. Most infected individuals—around 70% of women and 50% of men—experience no symptoms, earning the infection the nickname "silent epidemic." When symptoms do appear, they typically emerge several weeks after exposure, with an incubation period of two to six weeks during which the person can transmit the infection. In women, symptoms may include vaginal discharge, burning during urination, abnormal vaginal bleeding, abdominal pain, or painful intercourse. In men, symptoms can include penile discharge, burning with urination, or pain and swelling in one or both testicles. Untreated infections in women can ascend to the upper genital tract, causing pelvic inflammatory disease, which may lead to scarring, chronic pelvic pain, infertility, or ectopic pregnancy. In men, untreated chlamydia can spread to the testicles, causing epididymitis, which rarely may result in sterility. The infection can also affect the anus, eyes, throat, and lymph nodes. Repeated, untreated eye infections can lead to trachoma, a chronic conjunctivitis that was once a leading cause of blindness worldwide, though its contribution has declined. Transmission occurs through vaginal, anal, oral, or manual sex, and from an infected mother to her baby during childbirth. Eye infections can also spread through personal contact, flies, or contaminated towels in areas with poor sanitation. Diagnosis is often via screening, recommended annually for sexually active women under 25 and others at higher risk, including at the first prenatal visit. Testing can be performed on urine or swabs of the cervix, vagina, urethra, rectum, or mouth. Prevention involves abstinence, consistent condom use, or mutual monogamy with an uninfected partner. Chlamydia is curable with antibiotics, typically azithromycin or doxycycline; erythromycin o
- new cases in 2015
- WHO estimated 127 million new cases in 2016.
Lore & Background
Chlamydia is caused by the bacterium Chlamydia trachomatis, which only infects humans. Most infected people have no symptoms; when symptoms appear, they may occur weeks after infection. In women, symptoms can include vaginal discharge or burning with urination; in men, discharge from the penis, burning with urination, or testicular pain. The infection can spread to the upper genital tract in women, causing pelvic inflammatory disease, which may lead to infertility or ectopic pregnancy. Chlamydia can also cause eye infections (trachoma), which can lead to blindness if untreated, especially in the developing world. The word 'chlamydia' comes from the Greek χλαμύδα, meaning 'cloak'.
Reader's Guide
Its 'silent' nature—with at least 70% of infected women and 50% of infected men showing no symptoms—makes it a major public health challenge, as undetected infections can persist for months or years and lead to serious reproductive complications. Screening is recommended yearly for sexually active women under 25 and others at risk. Diagnosis uses nucleic acid amplification tests on urine or swabs. The infection is curable with antibiotics such as azithromycin or doxycycline; sexual partners should also be treated. Prevention includes abstinence, condom use, or mutual monogamy with an uninfected partner. Chlamydia's legacy includes its role in causing trachoma, a leading cause of blindness historically, and its association with reactive arthritis in young men.
Did You Know?
- Most people infected with chlamydia have no symptoms; it is known as the 'silent epidemic'.
- Chlamydia can cause trachoma, a common cause of blindness in the developing world.
- The word 'chlamydia' comes from the Greek χλαμύδα, meaning 'cloak'.
- Infants can acquire chlamydia during passage through the birth canal; about 30-50% develop conjunctivitis and 10-20% develop pneumonia.
Frequently Asked Questions
Who is Chlamydia?
Chlamydia is a sexually transmitted infection brought on by the bacterium Chlamydia trachomatis. It ranks among the most widespread STIs on the planet and is frequently dubbed the 'silent epidemic' because the vast majority of people carrying it never experience a single symptom.
What are Chlamydia's powers and how does it spread?
It can colonize the genitals, anus, eyes, throat, and lymph nodes, and it transmits through vaginal, anal, oral, or manual sex as well as from a mother to her baby during childbirth. Its stealth is its defining trait: most infected individuals feel perfectly healthy while the bacteria quietly establishes itself.
How does Chlamydia's story end if left unaddressed?
Untreated, it can escalate into pelvic inflammatory disease, infertility, or an ectopic pregnancy, turning a silent infection into a life-altering medical crisis. That potential for severe downstream damage is what makes early detection so critical.
Why is Chlamydia considered such a major player?
Its sheer scale is staggering: roughly 61 million new infections occurred worldwide in 2015, and it affects approximately 4.2% of women and 2.7% of men globally. In the United States alone, about 1.4 million cases were reported in 2014, underscoring how pervasive the threat is.
What is Chlamydia's greatest vulnerability?
Because most carriers are completely asymptomatic, the infection spreads invisibly, making routine screening the single most effective tool for catching it before complications set in. Its lack of obvious symptoms is both its superpower and its Achilles' heel.
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