Chlamydia is a common sexually transmitted infection caused by the bacterium Chlamydia trachomatis. It spreads through vaginal, anal, or oral sex with someone who has the infection. It can also pass from an infected mother to her baby during childbirth. The bacteria infect mucous membranes, including the cervix, urethra, throat, and rectum. Casual contact like hugging, sharing towels, or using the same toilet does not spread chlamydia.
What is chlamydia and what causes it?
Chlamydia is a bacterial infection. The cause is the bacterium Chlamydia trachomatis. These bacteria behave differently from many other bacteria. They live inside human cells, which makes them harder to detect and treat without the right antibiotics. Once inside a cell, the bacteria multiply and spread to other cells, causing inflammation and tissue damage over time.
The infection targets moist, warm areas of the body. These include the urethra (the tube urine passes through), the cervix, the rectum, and the throat. In women, the infection often begins in the cervix and can spread to the upper reproductive organs. In men, it typically starts in the urethra and can reach the epididymis (the tube that carries sperm).
How does chlamydia spread?
Chlamydia spreads almost exclusively through sexual contact. This includes vaginal, anal, and oral sex. The bacteria pass from an infected person to a partner through contact with infected genital fluids or mucous membranes. Condoms provide very good protection when used correctly and consistently, but they do not eliminate risk entirely because some infected areas may not be covered.
Another important route of transmission is from mother to baby during vaginal delivery. A newborn can be exposed to the bacteria in the birth canal, which can cause eye infections or pneumonia. This is why pregnant women are routinely tested for chlamydia early in pregnancy. If the infection is found, it is treated safely during pregnancy to protect the baby.
Chlamydia does not spread through casual contact. You cannot get it from a toilet seat, a swimming pool, or sharing a towel or bedding. The bacteria cannot survive long outside the human body. The only way to catch chlamydia is through direct sexual contact or from an infected mother to her newborn.
Who is at risk for chlamydia?
Anyone who is sexually active can get chlamydia. However, the infection is most common in people under age 25. Women in this age group are especially at risk because the cervix is more susceptible to infection. Other factors that increase risk include having multiple sexual partners, not using condoms consistently, and having a partner who has had chlamydia or other STIs in the past.
Men who have sex with men are also at elevated risk, particularly for rectal and throat infections. Routine screening is recommended for this population. The CDC and other major health organizations recommend annual chlamydia testing for all sexually active women under 25, older women with new or multiple partners, and men who have sex with men. Testing is also recommended for pregnant women.
What are the symptoms of chlamydia?
The majority of people with chlamydia have no symptoms. This is one of the reasons the infection spreads so easily. When symptoms do appear, they usually develop one to three weeks after exposure. In women, symptoms include abnormal vaginal discharge, burning during urination, lower abdominal pain, and bleeding between periods or after sex. In men, common symptoms are discharge from the penis, burning during urination, and pain or swelling in one testicle.
Rectal infections can cause discharge, bleeding, or pain in the anus. Throat infections rarely cause symptoms. Because so many people have no symptoms, they can unknowingly pass the infection to partners. This is why regular testing is important, especially for people at higher risk.
How is chlamydia treated?
Chlamydia is curable with antibiotics. The most common treatments are a single dose of azithromycin (taken as pills) or a seven-day course of doxycycline. Doxycycline is taken twice daily. Both are effective. Your doctor will choose based on your health history and other factors. It is important to take all prescribed antibiotics exactly as directed, even if symptoms disappear before finishing the course.
Your sexual partners need treatment too. If they are not treated, you can get the infection back. You should avoid sexual activity for seven days after finishing treatment, or until all symptoms have resolved if you received single-dose therapy. Retesting is recommended three to four months after treatment, because reinfection is common.
How can you prevent chlamydia?
The most effective way to prevent chlamydia is to use condoms correctly every time you have sex. Latex condoms are very effective when used from start to finish. Dental dams can help reduce risk during oral sex. Being in a mutually monogamous relationship with a partner who has been tested and is known to be negative also greatly reduces risk.
Regular screening is a key prevention tool. Because so many people have no symptoms, testing is the only reliable way to know if you have chlamydia. Early detection means early treatment, which stops further spread and prevents complications. The CDC recommends annual testing for all sexually active women under 25 and older women at risk. Talk to your healthcare provider about your personal risk and testing schedule.
What happens if chlamydia is left untreated?
Untreated chlamydia can lead to serious health problems. In women, the infection can spread from the cervix to the fallopian tubes and ovaries. This causes pelvic inflammatory disease (PID). PID can permanently scar the fallopian tubes, leading to chronic pelvic pain, ectopic pregnancy (a life-threatening condition where the pregnancy implants outside the uterus), and infertility. Up to 10 to 15 percent of women with untreated chlamydia develop PID.
In men, untreated chlamydia can cause epididymitis — inflammation of the tube that carries sperm. This can cause pain, swelling, and in rare cases infertility. Reactive arthritis, which affects joints, eyes, and the urethra, can also occur. For people with HIV, a chlamydia infection can increase the likelihood of transmitting the virus.
The bottom line: the infection is easy to treat and hard to detect on your own. Testing is straightforward, treatment is simple, and the consequences of delay can be permanent. If you are sexually active, talk with your provider about whether you should be tested.
Frequently Asked Questions
Can you get chlamydia from a toilet seat?
No. Chlamydia bacteria cannot survive on surfaces like toilet seats. The infection spreads only through direct sexual contact or from mother to baby during birth.
Can chlamydia go away on its own?
In some cases the body may clear the infection over months, but most people remain infected and contagious without treatment. Untreated infection can cause permanent damage, so antibiotics are always recommended.
How long after treatment is chlamydia no longer contagious?
You should avoid sex for seven days after completing treatment. If you received a single-dose antibiotic, wait seven days after taking it. If you took a seven-day course, wait until the course is finished and symptoms are gone.
Is it possible to have chlamydia for years without knowing?
Yes. Many people have no symptoms and an untreated infection can persist for months or years. This is why regular testing is important. The infection does not resolve on its own in most cases and can cause silent damage over time.
