Chlamydia spreads through sexual contact with an infected person. It passes through vaginal, anal, or oral sex, and you don’t need to experience any symptoms to transmit or contract it. With roughly 1.5 million cases reported in the United States in 2024 alone, it remains the most commonly reported bacterial sexually transmitted infection in the country.
How Chlamydia Spreads During Sex
The bacterium that causes chlamydia, called Chlamydia trachomatis, lives in the mucous membranes of the genitals, rectum, and throat. During vaginal or anal sex, the bacteria transfer between partners through direct contact with these infected tissues and the fluids they produce. Ejaculation does not need to occur for transmission to happen. Skin-to-skin contact with an infected area is enough.
Oral sex also carries risk. Giving oral sex to a partner with a genital or rectal infection can lead to chlamydia in the throat. A throat infection can then spread to other partners during oral sex. Throat infections often cause no noticeable symptoms, which makes them easy to pass along unknowingly.
You can get chlamydia in the mouth, throat, genitals, or rectum depending on the type of sexual contact involved. Rectal chlamydia can result from receptive anal sex or, in some cases, from the spread of a genital infection.
Why Most People Don’t Know They Have It
The biggest reason chlamydia spreads so easily is that most people who carry it feel perfectly fine. About 75% of women and 50% of men with chlamydia have no symptoms at all. That means a person can be infectious for weeks or months without any reason to suspect a problem.
When symptoms do appear, they typically show up several weeks after exposure. For women, this can include unusual vaginal discharge, burning during urination, or bleeding between periods. Men may notice discharge from the penis, burning when urinating, or pain in one or both testicles. Rectal infections can cause discharge, pain, or bleeding, though many rectal infections are also silent.
Because the infection so often flies under the radar, routine screening is the most reliable way to catch it. If you’ve had a new sexual partner or multiple partners, testing is the only way to know your status for certain.
Ways You Cannot Get Chlamydia
Chlamydia does not spread through casual contact. You will not get it from sharing food, hugging, kissing, holding hands, or sitting on a toilet seat. The bacterium can technically survive on surfaces for two to three hours under humid conditions, but this does not translate into a realistic transmission risk. The bacteria need direct contact with mucous membranes to establish an infection, and that contact essentially only happens during sex.
Swimming pools, hot tubs, and shared towels are not transmission routes either. If you haven’t had sexual contact with an infected person, your risk is effectively zero.
Transmission During Childbirth
The one non-sexual way chlamydia spreads is from a pregnant person to their baby during vaginal delivery. As the infant passes through the birth canal, the bacteria can infect the baby’s eyes or lungs, potentially causing eye infections or pneumonia in the first weeks of life. This is one reason prenatal screening for chlamydia is standard practice.
Re-infection Is Common
Having chlamydia once does not protect you from getting it again. Re-infection happens frequently, often because a person’s sexual partner was not treated at the same time. If you’re treated but your partner isn’t, the bacteria simply pass back to you the next time you have sex.
The CDC recommends retesting three months after treatment to check for repeat infection. Both you and any recent sexual partners need to complete treatment before resuming sexual activity. Otherwise, you’re likely starting the cycle over.
Who Is Most at Risk
Anyone who is sexually active can get chlamydia, but certain factors raise the odds. Having a new sexual partner, having multiple partners, or not using condoms consistently all increase risk. Younger adults tend to have higher rates of infection, partly because of these behavioral patterns and partly because of biological factors that make younger cervical tissue more susceptible.
Condoms reduce the risk of chlamydia significantly when used correctly during vaginal and anal sex, though they don’t eliminate it entirely since contact with surrounding skin can still occur. For oral sex, dental dams offer some protection, though they are used far less consistently in practice. The most reliable strategy combines barrier methods with regular screening, especially if your sexual partners change.