Chlamydia: A Comprehensive Overview

Chlamydia is one of the most common Sexually Transmitted Infections (STIs) worldwide, caused by the bacterium Chlamydia trachomatis. It is preventable and curable, spreading mainly through unprotected vaginal, oral, and anal sex.

1. What is Chlamydia?

Chlamydia is a common sexually transmitted infection (STI) that can occur in both men and women, caused by the bacterium Chlamydia trachomatis. It can infect sites such as:

• The urethra (inside the penis – the tube that carries urine out of the body).
• The cervix (in women).
• The rectum.
• The throat.
• The eyes (conjunctivitis, especially in newborns due to mother-to-child transmission).

Although it often has no clear symptoms, if left untreated, Chlamydia can lead to serious and permanent complications for reproductive health.

2. Epidemiology of Chlamydia

Chlamydia is the most reported STI globally, affecting millions of people each year.

• According to the World Health Organization (WHO) [1]:
  • An estimated 129 million new Chlamydia infections occurred globally in adults aged 15–49 years in 2020.
• According to the U.S. Centers for Disease Control and Prevention (CDC) [2]:
  • In 2023, over 1.6 million cases of Chlamydia were reported in the United States. The incidence rate was nearly 500/100,000, with the highest-risk group being adolescents and young adults, particularly those aged 15–24, who accounted for 55.8% of total cases.
• In Vietnam [3, 4, 5]:
  • Studies and reports in Vietnam show that Chlamydia is one of the common STIs.
  • The estimated general prevalence rate among adults infected with Chlamydia is 2.3%; in reality, the rate may be higher due to limited survey data and the omission of many asymptomatic cases, as well as incomplete sample collection.
  • According to statistics from worldpopulationreview.com, the number of Chlamydia cases in Vietnam in 2021 was approximately 2,600.
  • The prevalence rate of Chlamydia in high-risk groups (such as female sex workers, men who have sex with men-MSM) can be up to over 20%.
  • There is a high rate of co-infection between Chlamydia and gonorrhea, as well as an important finding in a 2022 study in Hanoi on the HIV pre-exposure prophylaxis (PrEP) program reporting a Chlamydia prevalence rate of up to 20.4%.
  • Screening for Chlamydia in pregnant women and high-risk groups remains a challenge, leading to a high risk of mother-to-child transmission and long-term complications.

3. Routes of Chlamydia Transmission [1, 6, 9]

Chlamydia is primarily transmitted through unprotected sexual contact with an infected person. The main routes of transmission include:

• Vaginal, Anal, or Oral Sex: These are the most common routes of infection, leading to Chlamydia infection in the genitals, rectum, or throat.
• Mother-to-Child: Pregnant women with Chlamydia can transmit the bacteria to their baby during childbirth, causing eye infections (conjunctivitis) and pneumonia in newborns.
• Direct Contact with Secretions: Although less common, direct contact with infected secretions (e.g., infected hand touching the eye) can also cause infection.

Chlamydia is not transmitted through casual contact such as hugging, kissing, or sharing toilets, bathtubs, towels, or dishes… because the Chlamydia bacteria are fragile when outside the host cell and are quickly destroyed by common disinfectants.

4. Symptoms of Chlamydia [1,6,9]

Chlamydia is often called the ‘silent disease’ because the majority of infected people (about 70% of women and 50% of men) do not have any obvious symptoms. This makes early diagnosis and infection control difficult. When symptoms do occur, they usually appear days to weeks after exposure to the bacteria.

4.1. Symptoms in Men

In men, symptoms, if present, are usually related to the genitourinary tract, including:

• Dysuria (Painful Urination): Stinging, pain, or a burning sensation when urinating.
• Discharge from the Penis: Milky white or clear discharge that may contain pus, often scant and hard to notice.
• Itching or Discomfort at the Urethral Opening (Meatus, Urinary Opening): Urethritis.
• Testicular Pain or Swelling: Usually only affects one testicle (epididymitis), less common.

4.2. Symptoms in Women 

Women often have no symptoms or have mild symptoms that are easily mistaken for other gynecological infections, bladder inflammation, or a Urinary Tract Infection (UTI). Symptoms include:

• Dysuria (Painful Urination): Stinging, pain, or a burning sensation when urinating.
• Increased Vaginal Discharge: Discharge may be yellow and have a foul odor.
• Itching or Burning Sensation: In and around the vagina.
• Abnormal Vaginal Bleeding: Bleeding between menstrual periods, after sexual intercourse, or heavier than normal menstrual flow.
• Lower Abdominal or Pelvic Pain.
• Pain During Sexual Intercourse (Dyspareunia).

4.3. Symptoms in Other Locations

Chlamydia can infect and cause symptoms in many other locations besides the genitals, such as:

• Rectum: Rectal pain, discharge, bleeding, or anal itching.
• Throat: Chlamydia infection in the throat is often asymptomatic, but may cause a sore throat, pharyngitis, or swollen lymph nodes in the neck.
• Eyes: Conjunctivitis (red, itchy eyes, discharge), often occurring due to self-inoculation from the hands or mother-to-child transmission.

5. Risk Factors for Chlamydia Infection [1,6,9]

Factors that significantly increase the risk of contracting Chlamydia include:

• Having Multiple or New Sexual Partners: A higher number of partners or new partners with an unknown sexual history will increase the risk of exposure to an infected person.
• Inconsistent and Correct Condom Use: Condoms are an effective measure to prevent Chlamydia transmission.
• History of Other Sexually Transmitted Infections (STIs): Having had other STIs may increase the likelihood of contracting Chlamydia.
• Sexual Contact with a Partner Known or Suspected to Have Chlamydia.
• Belonging to the Young Age Group (15–24 years old): This age group has the highest incidence of Chlamydia infection.
• Men who have sex with men (MSM).

6. Complications [1,6,9]

If not diagnosed and treated promptly, Chlamydia can cause serious and permanent complications, affecting reproductive and overall health.

• In Women:
  • Pelvic Inflammatory Disease (PID): The infection can spread to the uterus, fallopian tubes, and ovaries, causing chronic abdominal pain, infertility, and an increased risk of ectopic pregnancy.
  • Infertility: Permanent damage to the fallopian tubes can prevent the egg from meeting the sperm.
  • Ectopic Pregnancy: A fertilized egg develops outside the uterus, which can be life-threatening.
• In Men:
  • Epididymitis: Infection of the tube that holds the testicles, causing pain and swelling. In some rare cases, it can lead to infertility.
  • Urethritis: Chronic urinary tract infection can cause chronic pelvic pain, and prostatitis.
• Other Complications:
  • Reactive Arthritis (Reiter’s Syndrome): Some people may develop arthritis, conjunctivitis, and urethritis after Chlamydia infection.
  • Increased Risk of HIV Infection: Chlamydia infection can increase the likelihood of contracting or transmitting HIV.
• In Newborns:
  • Conjunctivitis (Eye Infection): Serious eye infection that can lead to blindness if untreated.
  • Pneumonia: Lung infection in newborns.

7. Diagnosis [7,8,9]

When any suspicious symptoms are present, it is necessary to promptly visit reputable healthcare facilities for testing and early diagnosis. Early treatment increases the chance of a complete cure and minimizes dangerous complications. Chlamydia diagnosis is usually performed through the following tests:

• Nucleic Acid Amplification Tests (NAATs):
  • As an NAAT method, PCR testing for Chlamydia has high sensitivity and specificity, making it the gold standard for diagnosis.
  • It can be applied to various types of specimens such as: vulvar, vaginal, cervical, urethral discharge and urine, and throat.
  • It can also simultaneously test for Chlamydia and gonorrhea, as well as some other STI agents in the same specimen.
• Other Tests: Although less common, some other methods such as cell culture or enzyme immunoassay (EIA) may also be used.
• Screening for Other STIs: Chlamydia infection carries the risk of concurrent gonorrhea infection, as well as other sexually transmitted infections (syphilis, HIV, etc.), so early screening is recommended.

8. Treatment [7,8,9]

Chlamydia can be completely cured with antibiotics. Timely and correct treatment according to the regimen is very important to prevent complications and spread. Oral Doxycycline remains the preferred and effective drug for Chlamydia infection today. For pregnant women, Doxycycline is contraindicated and should be replaced with oral Azithromycin.

• Important Notes on Treatment:
  • Do Not Self-Treat: Self-medication or non-adherence to the regimen can lead to treatment failure and increased risk of drug resistance.
  • Partner Treatment: All sexual partners within 60 days before diagnosis also need to be tested and treated to prevent reinfection and spread of the disease.
  • Avoid Sexual Intercourse: Patients should abstain from all sexual activity until both they and their partner have completed treatment and the symptoms have completely disappeared (usually 7 days after the single-dose antibiotic or after completing the 7-day course).

The majority of post-treatment infections are not due to treatment failure but rather reinfection caused by the partner not being treated or starting sexual activity with a new infected partner. Post-treatment follow-up is very important to ensure the disease has been completely cured and to detect early cases of reinfection:

• Retesting is required after 3–4 weeks of treatment in pregnant women.
• All patients, including pregnant women, who have been treated for Chlamydia should be retested about 3 months after treatment, regardless of whether they believe their partner has been treated.
• Counseling and Education:
  • Patients need to be counseled on the importance of informing and treating their sexual partners to avoid reinfection and spread.
  • Education on STI prevention measures, including correct and consistent condom use.
  • Encouragement to be tested for other STIs if at risk, as having one STI increases the risk of contracting others.

9. Prevention

Chlamydia prevention is key to controlling the spread of the disease and protecting individual health. Effective prevention measures include:

• Practicing Safe Sex:
  • Consistent and Correct Condom Use: This is the most effective measure to prevent the transmission of Chlamydia and other STIs during vaginal, anal, or oral sex.
  • Limiting the Number of Sexual Partners and Avoiding Sex with New Partners of Unknown History: Reducing the number of partners will reduce the risk of exposure to an infected person.
  • Do not share sex toys, if you do, they should be thoroughly cleaned, and a condom should be used before use.
• Timely Screening and Treatment:
  • Regular STI Testing: Proactively check and test your health and your partner’s health regularly to detect sexually transmitted diseases early. Especially if you have multiple partners or are at high risk, get tested for STIs regularly, including Chlamydia.
  • Chlamydia Screening for Pregnant Women: This is an extremely important measure to prevent transmission to the newborn.
  • Immediate Treatment: If you or your partner are diagnosed with Chlamydia, seek immediate treatment and adhere to the doctor’s regimen.
• Education and Awareness:
  • Open Discussion with Your Partner: Discuss your STI history and testing before sexual intercourse. Proactively choose safe partners and agree with your partner on the use of protective measures during sex.
  • Raising Awareness of Sexual Health: Understanding STIs and how to prevent them is crucial.

This article is written by BS. CKI. Võ Nguyễn Duy Hoà, a specialist in General Surgery, Urology, and Andrology, to provide fundamental knowledge about Chlamydia, its transmission methods, recognizable signs, the importance of early diagnostic testing and treatment, as well as effective prevention. It helps you understand correctly to proactively protect your health and the community.

Reference

1. [1]. Chlamydia. https://www.who.int/news-room/fact-sheets/detail/chlamydia
2. [2]. National Overview of STIs in 2023. https://www.cdc.gov/sti-statistics/annual/summary.html
3. [3]. Bệnh do Chlamydia Trachomatis
   https://dalieu.vn/benh-do-chlamydia-trachomatis-d3386.html
4. [4]. STD Rates by Country in 2021 – worldpopulationreview.com
   https://worldpopulationreview.com/country-rankings/std-rates-by-country
5. [5]. Routine testing for chlamydia and gonorrhea in an HIV preexposure prophylaxis program in Hanoi, Vietnam: implications for low- and middle-income countries – PubMed. https://pubmed.ncbi.nlm.nih.gov/40334065/
6. [6]. About Chlamydia
   https://www.cdc.gov/chlamydia/about/index.html#cdc_disease_basics_testing_screening-testing-and-diagnosis
7. [7]. Sexually Transmitted Infections Treatment Guidelines, 2021
   https://www.cdc.gov/std/treatment-guidelines/STI-Guidelines-2021.pdf
8. [8]. Updated recommendations for the treatment of Neisseria gonorrhoeae, Chlamydia trachomatis and Treponema pallidum (syphilis), and new recommendations on syphilis testing and partner services
   https://iris.who.int/bitstream/handle/10665/378213/9789240090767-eng.pdf?sequence=1
9. [9]. Quyết định 5169/QĐ-BYT 2021 hướng dẫn chẩn đoán và điều trị bệnh Chlamydia Trachomatis
   https://thuvienphapluat.vn/van-ban/The-thao-Y-te/Quyet-dinh-5169-QD-BYT-2021-huong-dan-chan-doan-va-dieu-tri-benh-Chlamydia-Trachomatis-494083.aspx