Chlamydia spreads through sexual contact with an infected person. You can get it from vaginal, anal, or oral sex without a condom, and roughly 1.5 million cases are reported in the U.S. each year. Because the majority of infections cause no symptoms at all, many people pass it on without knowing they have it.
Vaginal and Anal Sex Are the Main Routes
The most common way chlamydia spreads is through unprotected vaginal or anal intercourse. The bacterium lives in infected sexual fluids and thrives in mucous membranes, the moist tissue lining the cervix, urethra, and rectum. During sex, the bacteria transfer from one person’s infected tissue to another’s. You don’t need to experience ejaculation for transmission to occur; direct contact between mucous membranes is enough.
Rectal chlamydia can develop from receptive anal sex, but it can also spread from a vaginal infection to the rectum without anal sex being involved. This means someone with a genital infection can end up with a rectal one through the body’s own anatomy, not just through a specific sexual act.
Oral Sex Carries Risk Too
Chlamydia can infect the throat after giving oral sex to a partner who has a genital or rectal infection. It’s possible to carry the infection in more than one site at the same time, so someone could have chlamydia in both the throat and genitals simultaneously. Throat infections may produce mild symptoms or none at all, and a person with chlamydia in the throat can spread it to a partner’s genitals during oral sex.
Comparing the exact risk of oral transmission to vaginal or anal transmission is difficult because most people who have oral sex also have other types of sex, making it hard to isolate which act caused a given infection.
You Can Spread It to Your Own Eyes
If you touch infected genital secretions and then touch your eyes, the bacteria can cause chlamydial conjunctivitis, a painful eye infection. This hand-to-eye route is the typical way adults develop chlamydia in the eye. It’s not common, but it’s a real risk for anyone with an active genital infection who isn’t careful about hand hygiene.
Passing It to a Newborn During Birth
A pregnant person with chlamydia can transmit the infection to their baby during vaginal delivery as the infant passes through the birth canal. In newborns, chlamydia can cause eye infections and pneumonia. This is one reason routine chlamydia screening is part of standard prenatal care.
Ways You Cannot Get Chlamydia
Chlamydia cannot survive long outside the human body. The bacterium needs the warm, moist environment of living mucous membrane tissue to stay viable. You will not get chlamydia from a toilet seat, a shared towel, a swimming pool, or casual contact like hugging or sharing food. Even if infected fluid landed on a surface, the bacteria would need to reach suitable tissue like the cervix, urethra, or eye before drying out, which is essentially impossible in everyday situations. Skin contact alone is not sufficient for infection.
Most Infections Have No Symptoms
About 75% of women and 50% of men with chlamydia experience no symptoms whatsoever. This is the single biggest reason it spreads so effectively. People who feel perfectly healthy can carry and transmit the infection for weeks or months without knowing. When symptoms do appear, they typically include unusual discharge, burning during urination, or pain during sex, but the absence of symptoms is far more common than their presence.
This asymptomatic nature also explains why regular screening matters for sexually active people, particularly those under 25 or with new partners.
Reinfection Is Extremely Common
Having chlamydia once does not protect you from getting it again. Research from the California Department of Public Health shows that as many as 20% of women test positive again within six months of being treated. The most common reason is having sex with a partner who wasn’t treated at the same time. If only one person in a sexual partnership takes antibiotics, the untreated partner simply passes the bacteria right back.
This is why treatment needs to cover both you and any recent sexual partners. Waiting to have sex until everyone involved has completed treatment prevents the cycle of reinfection that makes chlamydia so persistent.
How Condoms Reduce the Risk
Consistent condom use significantly lowers your chances of getting chlamydia, though it doesn’t eliminate the risk entirely. A study published in the American Journal of Epidemiology found that among people with a known infected partner, consistent condom use was associated with a 58% reduction in chlamydia and gonorrhea infections. That’s a meaningful drop, but it also means condoms aren’t perfect protection, partly because the bacteria can infect areas a condom doesn’t cover, like the rectum or throat.
Using condoms every time, getting tested regularly, and making sure partners are tested and treated when needed are the most effective combination for avoiding chlamydia. Since the infection is easily cured with antibiotics, catching it early through screening prevents both long-term complications and further spread.