Chlamydia: Symptoms, Causes & Treatment

Chlamydia trachomatis is the most prevalent bacterial sexually transmitted infection (STI) globally, with the WHO estimating over 127 million new cases annually. Incidence is highest in young people under 25, particularly women. The defining clinical challenge is the high rate of asymptomatic infection: 70–80% of infected women and 50% of infected men have no symptoms, allowing silent transmission and untreated progression to serious reproductive complications.

In women, Chlamydia infects the endocervix and can ascend to cause pelvic inflammatory disease (PID) — salpingitis, endometritis, and tubo-ovarian abscess — in 10–15% of untreated cases. Sequelae include chronic pelvic pain, ectopic pregnancy, and tubal factor infertility. In men, it causes urethritis and may spread to the epididymis (epididymo-orchitis), risking fertility. Reactive arthritis (Reiter syndrome — urethritis, conjunctivitis, arthritis) is an uncommon but recognized complication. Neonatal transmission during delivery causes conjunctivitis and pneumonia in the newborn.

Nucleic acid amplification tests (NAAT) on urine or self-collected vaginal swabs are the gold standard for diagnosis, with >95% sensitivity and specificity. Treatment with azithromycin 1 g single dose or doxycycline 100 mg twice daily for 7 days is highly effective. Partner notification and treatment are essential to prevent reinfection. Annual screening is recommended for all sexually active women under 25 and older women with risk factors.

• Most common: NO symptoms (70–80% of women, 50% of men) — silent transmission
• Women: mucopurulent vaginal discharge, intermenstrual bleeding, postcoital bleeding, dyspareunia
• Men: urethral discharge (clear to purulent), dysuria, testicular pain or swelling (epididymo-orchitis)
• PID: bilateral lower abdominal pain, fever, cervical motion tenderness on examination
• Rectal infection: anorectal pain or discharge in those who practice receptive anal sex

• Sexual transmission of Chlamydia trachomatis via vaginal, anal, or oral sex
• Vertical transmission from infected mother to neonate during delivery
• Risk factors: multiple sexual partners, inconsistent condom use, age under 25, prior STI, male-male sexual contact

Nucleic acid amplification test (NAAT) is the gold standard: >95% sensitivity and specificity from first-void urine, self-collected vaginal swab, or urethral swab in men. Endocervical swab adds sensitivity in women. Culture is rarely used clinically. Annual NAAT screening is recommended for all sexually active women under 25; screen men who have sex with men more frequently. Co-test for gonorrhea, syphilis, and HIV given frequent co-infection.

First-line: azithromycin 1 g single oral dose (preferred for adherence) OR doxycycline 100 mg twice daily for 7 days (preferred for PID and rectal infection). Pregnant women: azithromycin or amoxicillin (doxycycline contraindicated). Sexual abstinence for 7 days after single-dose treatment or until 7-day course is completed. Partner notification and expedited partner therapy are essential. Test of cure (retest in 3–6 months) recommended due to high reinfection rates.

• Pelvic inflammatory disease (PID): leading to tubal scarring, ectopic pregnancy, tubal factor infertility, and chronic pelvic pain
• Epididymo-orchitis: pain, swelling, and potential male infertility
• Reactive arthritis (Reiter syndrome): urethritis + conjunctivitis + arthritis triad
• Neonatal conjunctivitis and pneumonia from vertical transmission
• Increased HIV transmission susceptibility due to mucosal inflammation

• Consistent condom use reduces Chlamydia transmission by approximately 50–70%
• Annual NAAT screening for all sexually active women under 25 and high-risk older individuals
• Partner notification and treatment for all confirmed cases to break transmission chains
• Expedited partner therapy (EPT) — providing treatment to the partner without requiring a separate clinical visit