What is Chlamydia?

Chlamydia is a common sexually transmitted infection (STI) caused by the bacterium Chlamydia trachomatis. It is one of the most prevalent STIs globally and in Hong Kong, particularly among sexually active young adults aged 15–24 . Many infected individuals do not show symptoms, making it easy to unknowingly transmit the infection to sexual partners. If left untreated, chlamydia can lead to serious health complications, including infertility and chronic pelvic pain.

How Common is Chlamydia in Hong Kong?

According to a population-based study, the overall prevalence of chlamydia in Hong Kong is approximately 1.4% among residents aged 18–49. However, certain groups are at higher risk:

• Young women aged 18–26 have a prevalence of 5.8%.
• Older women aged 40–49 also show a higher prevalence, forming a "U-shape" disease burden.
• Individuals who live alone or have traveled outside Hong Kong in the past 12 months are at increased risk .

Sexually transmitted infections, including chlamydia, are not notifiable in Hong Kong, meaning actual cases are likely underreported .

Symptoms of Chlamydia

Asymptomatic Cases

Up to 70% of people with chlamydia experience no symptoms, especially in the early stages. This makes regular testing crucial for sexually active individuals .

Symptoms in Women

• Unusual vaginal discharge (e.g., yellow or gray with a foul odor).
• Pain or burning during urination.
• Bleeding between periods or after sex.
• Lower abdominal pain .

Symptoms in Men

• Watery or mucus-like discharge from the penis.
• Pain or burning during urination.
• Swelling or pain in the testicles .

Other Symptoms

• Rectal pain, discharge, or bleeding (if infected through anal sex).
• Sore throat (if infected through oral sex).
• Eye infections (if contaminated fluids touch the eyes) .

Complications of Untreated Chlamydia

In Women

• Pelvic Inflammatory Disease (PID): Infection of the uterus, fallopian tubes, and ovaries, which can cause chronic pain and infertility.
• Ectopic Pregnancy: A life-threatening condition where a fertilized egg implants outside the uterus.
• Transmission to Newborns: During childbirth, chlamydia can cause eye infections or pneumonia in babies .

In Men

• Epididymitis: Inflammation of the testicles, potentially leading to infertility.
• Reactive Arthritis: Joint inflammation accompanied by eye and urethra irritation .

REF:
1. World Health Organization. Report on global sexually transmitted infection surveillance 2018.
2. Chlamydia Trachomatis Infections: Screening, Diagnosis, and Management, Am Fam Physician. 2012 Dec 15;86(12):1127-1132.
3. Fleming DT, Wasserheit JN. From epidemiological synergy to public health policy and practice: the contribution of other sexually transmitted diseases to sexual transmission of HIV infection. Sexually transmitted infections 1999;75:3-17.