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What you should know about Chlamydia
Chlamydia is one of the most common sexually transmitted infections (STIs). It is caused by Chlamydia trachomatis, an obligate intracellular bacterium that can infect the genital, rectal and ocular tissues. Transmission occurs through sexual contact involving the penis, vagina, mouth or anus of an infected person. An untreated cervical infection can also be transmitted from mother to newborn during childbirth.
The infection is often difficult to recognise because most people have no symptoms. When symptoms do occur, they vary according to the site of infection. In women, chlamydia may cause abnormal vaginal discharge, bleeding from the cervix, increased urinary frequency and pain when urinating. In men, symptoms may include urethral discharge, dysuria and testicular pain. Rectal infection can cause proctitis, with rectal pain, discharge or bleeding. Chlamydia can also infect the eyes and cause conjunctivitis following sexual transmission.
Only a minority of infected people develop noticeable symptoms. Estimates suggest that symptoms occur in around 10% of infected men and between 5% and 30% of infected women. The absence of symptoms, however, does not mean that the infection is harmless. Chlamydia can persist unnoticed and, when left untreated, may lead to complications that appear much later.
Pelvic inflammatory disease
One of the most important complications of untreated chlamydia is pelvic inflammatory disease (PID), an infection affecting the upper female reproductive tract. The infection can move upwards from the vagina and cervix into the uterus, fallopian tubes and surrounding reproductive tissues. Other microorganisms can also contribute to PID.
The proportion of women with untreated chlamydia who subsequently develop PID varies between studies, but has been estimated at approximately 16%. PID may be completely asymptomatic or present with relatively mild symptoms. Possible signs include lower abdominal or pelvic pain, fever, abnormal vaginal discharge, pain or bleeding during sexual intercourse, painful or frequent urination, and bleeding between menstrual periods.
Diagnosis usually combines the medical history, physical examination and laboratory or imaging findings. During a pelvic examination, cervical motion, uterine or adnexal tenderness may indicate inflammation. Other findings can include an increased number of white blood cells in vaginal secretions, elevated C-reactive protein and a friable or easily irritated cervix. In some cases, further investigation may involve endometrial biopsy, transvaginal ultrasound or magnetic resonance imaging.
PID is treated with broad-spectrum antibiotics covering the pathogens most likely to be involved. Treatment can eliminate the infection, but it cannot reverse tissue damage that has already occurred. Completing the prescribed treatment is therefore important, as is the simultaneous treatment of sexual partners when indicated, both to prevent reinfection and to interrupt transmission.
Infertility
The reproductive consequences of untreated chlamydia are particularly important because damage can develop without obvious symptoms. PID is associated with an increased risk of infertility, especially after repeated episodes or severe inflammation of the fallopian tubes. Importantly, infertility may also follow subclinical PID, meaning that significant reproductive damage can occur even when the person has never experienced clear symptoms.
This is one of the main reasons why early detection and treatment of chlamydia matter. Screening and testing can identify an infection before complications have had an opportunity to develop.
Ectopic pregnancy
Inflammation caused by chlamydia can damage the fallopian tubes and increase the risk of ectopic pregnancy. This occurs when a fertilised egg implants outside the main cavity of the uterus, most commonly within a fallopian tube.
An ectopic pregnancy cannot develop normally and can become life-threatening if the affected tube ruptures. Early symptoms may include pelvic pain, light vaginal bleeding and an unusual urge to have a bowel movement. If rupture occurs, severe internal bleeding can lead to fainting, shock and a medical emergency.
Preterm delivery
Chlamydial infection during pregnancy has also been associated with an increased risk of preterm birth. Studies have reported approximately a four-fold increase in deliveries occurring before 32 weeks of pregnancy and a two- to three-fold increase in deliveries before 35 weeks.
Premature birth can have consequences for several developing organ systems, including the lungs, heart and brain. Difficulties with temperature regulation, digestion and metabolism may also occur. Depending on the degree of prematurity, longer-term consequences can include cerebral palsy, learning difficulties, impaired vision or hearing and other chronic health problems.
Infection in newborns
An untreated chlamydial infection during pregnancy can be transmitted to the newborn during childbirth. Estimates suggest a transmission risk of approximately 50–70%.
Newborns exposed to the infection are particularly vulnerable to conjunctivitis and pneumonia. Conjunctivitis has been reported in approximately 18–44% of exposed infants, while pneumonia occurs in around 3–16%. Without treatment, chlamydial conjunctivitis can persist for months and may result in scarring of the conjunctiva or cornea.
For this reason, identifying and treating chlamydia during pregnancy is important not only for the health of the mother, but also for preventing infection and complications in the newborn.
Epididymitis
In men, chlamydia is one of the most common infectious causes of epididymitis, together with gonorrhoea. Epididymitis involves inflammation of the epididymis, the structure connected to the testicle where sperm mature and are stored. It may cause pain and swelling and can sometimes extend to the testicle, a condition known as epididymo-orchitis.
Treatment involves antibiotics directed at the underlying infection. Sexual partners may also require assessment and treatment to reduce the risk of reinfection.
Male fertility
Chlamydial infection has also been associated with changes affecting sperm and male reproductive function. Inflammation associated with the infection may interfere with sperm quality and fertility. Appropriate antibiotic treatment can help resolve the infection and may improve reproductive parameters in affected individuals.
HIV
Chlamydia can increase susceptibility to HIV infection by producing inflammation and, in some cases, lesions in the genital or rectal tissues. These changes can make it easier for HIV to enter the body during sexual exposure.
Among people living with HIV, untreated chlamydia and other STIs may also increase the likelihood of HIV transmission to sexual partners. Effective HIV treatment, however, prevents sexual transmission of HIV when viral suppression is maintained.
Reactive arthritis
In a small number of cases, chlamydial infection can trigger reactive arthritis, an inflammatory condition affecting the joints that develops after an infection elsewhere in the body. Chlamydia is one of the recognised infectious triggers of reactive arthritis.
The condition illustrates an important aspect of chlamydia: the consequences of an STI are not necessarily confined to the site where the infection began. An infection that produces little or no genital symptoms can, in some circumstances, have effects elsewhere in the body.
Why early detection matters
Chlamydia is therefore not simply an infection that causes temporary genital symptoms. Its significance lies partly in what can happen while it remains unnoticed. Testing makes it possible to identify infection before symptoms appear or complications develop, while treatment can eliminate the infection and reduce the risk of onward transmission.
This is also where ENDO can play a practical role. By bringing sexual-health information, testing, partner communication and access to prevention resources into the same platform, ENDO can make the steps between recognising a potential risk, getting tested, informing partners and taking preventive action easier to navigate. The aim is not to turn sexual health into a constant source of concern, but to make responsible action simpler and more routine. In this context, ENDO can help transform STI prevention from something people respond to only after symptoms or exposure into an ordinary part of sexual healthcare.
