Chlamydia (kluh-MID-ee-uh) is a common sexually transmitted illness. You may not know you have chlamydia because many people never develop the signs or symptoms, which may include genital pain and a discharge from the vagina or penis.


Chlamydia affects both men and women and occurs in all age groups, though it's most prevalent among young women. Chlamydia isn't difficult to treat once you know you have it. If it's left untreated, however, chlamydia can lead to more-serious health problems.


It is the most common sexually transmitted disease (STD) in the United States, with over 2.8 million affected individuals each year. Among adults, about 5% of the population is estimated to be infected. Among sexually active adolescent females, about 10% are infected.


Infection with chlamydia is most commonly found among the following groups:


  • Young adults (24 years and younger).
  • People living in urban areas.
  • African Americans.
  • Those with lower social and economic status.


Symptoms of chlamydia infection may depend on gender.


Chlamydia Symptoms in Women 


  • No symptoms in 70% to 80% of cases (One study found that 3% of a sample of young adults 18 to 35 years of age  had untreated chlamydia).
  • Bleeding after sexual relations or between menstrual periods.
  • Lower abdominal pain and burning pain during urination.
  • Discharge from the vagina.


Chlamydia Symptoms in Men


  • Like women, men who are infected may not show symptoms. Estimates of those with no symptoms range from 25% to 50% of infected men. 
  • Discharge from the penis.
  • Pain, burning during urination.
  • Inflammation or infection of a duct in the testicles, tenderness or pain in the testicles.


Chlamydia is caused by bacteria and is most commonly spread through vaginal, oral and anal sex. It's also possible for a mother to spread chlamydia to her child during delivery, causing pneumonia or a serious eye infection in her newborn.


Chlamydia is an infection caused by the bacterium Chlamydia trachomatis.


The infection is transmitted in 2 ways:


  • From one person to another through sexual contact (oral, anal, or vaginal).
  • From mother to child with passage of the child through the birth canal. Chlamydia can cause pneumonia or serious eye infections in a newborn, especially among children born to infected mothers in developing countries.


Chlamydia is treated with antibiotics. You may be asked to take your medication in a one-time dose, or you may need to take the medication daily or multiple times a day for five to 10 days.


In most cases, the infection resolves within one to two weeks. During that time you should abstain from sex. Your sexual partner or partners also need treatment even though they may not have signs or symptoms.


Otherwise, the infection can be passed back and forth between sexual partners. Having chlamydia or being treated for it in the past provides no immunity against possible reinfection in the future.


Tests and diagnosis


Because of the chance of other health problems if you contract chlamydia, ask your doctor how often you should have chlamydia screening tests if you're at risk. The Centers for Disease Control and Prevention recommends chlamydia screening for:

  • Sexually active women age 25 or younger. The rate of chlamydia infection is highest in this group, so a yearly screening test is recommended. Even if you've been tested in the past year, get tested when you have a new sex partner.
  • Pregnant women. You should be tested for chlamydia during your first prenatal exam. If you have a high risk of infection — from changing sex partners or from your regular partner's possible infection — get tested again later during the pregnancy.
  • Women and men at high risk. Consider frequent chlamydia screening if you have multiple sex partners or if you don't always use a condom during sex. Other markers of high risk are current infection with another sexually transmitted illness and possible exposure to any STI through an infected partner.


Screening and diagnosis of chlamydia is relatively simple.


Tests include:


  • A swab. For women, your doctor may take a swab of the discharge from your cervix for culture or antigen testing for chlamydia. This can be done at the same time your doctor does a routine Pap test. For men, your doctor may insert a slim swab into the end of your penis to get a sample from the urethra. In some cases, your doctor may swab the anus to test for the presence of chlamydia.
  • A urine test. A sample of your urine analyzed in the laboratory may indicate the presence of this infection.
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