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Chlamydia infection is a common sexually transmitted infection in humans caused by the bacterium Chlamydia trachomatis. The term Chlamydia infection can also refer to infection caused by any species belonging to the bacterial family Chlamydiaceae. Chlamydia trachomatis is found only in humans. It is a major infectious cause of human genital like Pelvic inflammatory disease and eye disease, the World Health Organization estimates that it accounted for 15% of blindness cases in 1995, but it reduced to 3.6% in 2002.


How common

In 2014, 1,441,789 cases of chlamydia were reported to Centers for Disease Control and Prevention from 50 states and the District of Columbia. However, it is estimated that almost 3 million cases actually occurred and as many as one in 10 adolescent females test positive for chlamydia. A large number of cases are not reported because most people with chlamydia are asymptomatic and do not seek testing. Chlamydia is 80% among young people, around 15-29 year old. This disease is more commonly reported in women. The reported case rate among females was about two times (2:1 ratio) the case rate among men, likely reflecting a larger number of women screened for this infection. The lower rates among men also suggest that many of the sex partners of women with chlamydia are not receiving a diagnosis of chlamydia or being reported as having chlamydia.


According to the World Health Organization, there were 4.3 million females and 4 million males in Africa region, 4.2 million females and 3 million males in Asia, 8.3 million females and 12.3 million males in Europe got infected by Chlamydia.

Chances of being infected

The risk of Infection (%) from One Unprotected Encounter for women is 40% and 20% for men. This means if a woman has unprotected sex with a man who has Chlamydia, she has a 40% percent risk of becoming infected. In the opposite case, the risk is 20% percent.

How to detect if someone has it

Chlamydia - Detect

Chlamydia symptoms are similar to gonorrhea, but are often less noticeable. If someone has chlamydia, s/he may get infection in the throat, which can lead to painful swallowing, a cough, and a fever; also if a woman has symptoms, she may have pain during sex, bleeding after sex or between periods, or unusual vaginal discharge (yellowish or whitish fluid). Unfortunately, Chlamydia may also not produce symptoms in men, when they do have it, it may appear as an unusual discharge like clear or cloudy, sticky fluid at the opening of the penis.


Despite its prevalence, no vaccine exists to protect against infection with the sexually transmitted bacterium Chlamydia trachomatis. In large multi-nation study circumcision is able to reduce about 82% of the risk to get Chlamydia. In the meantime, the best method to prevent Chlamydia is wearing a condom.

Condom effectiveness

According to a study titled “Condom effectiveness for prevention of Chlamydia trachomatis infection” published by the STD Journal, consistent condom use was significantly associated with a 90% reduction in the prevalence of Chlamydia trachomatis infection among their respondents.


Chlamydia can usually be effectively treated with antibiotics. More than 95% of people will be cured if they take their antibiotics correctly.
The most commonly prescribed antibiotics for chlamydia are:

  • Azithromycin – given as two or four tablets at once
  • Doxycycline  – given as two capsules a day for a week
  • Ofloxacin 300 mg twice daily for 7 days and levofloxacin 500 mg once daily for 7 days for alternative

Best sources for more information


  • Chlamydia infection




  • Chlamydia – CDC Fact Sheet (Detailed)



  • Sexually transmitted infections and Chlamydia



  • Chlamydia: detection, treatment and prevention




  • Chlamydia (genital) – including symptoms, treatment and prevention



  • A mucosal vaccine against Chlamydia trachomatis generates two waves of protective memory T cells



  • Chlamydia – Treatment




  • Chlamydia in Women



The risk chart is the heart of this guide, and it can be found here

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