Chlamydia is primarily a sexually transmitted infection, but it is not exclusively spread through sex. The bacterium responsible, Chlamydia trachomatis, can also pass from mother to baby during childbirth, spread from one body site to another through touch, and in some forms cause eye infections transmitted through hands, shared fabrics, and even flies. There are also related chlamydia species that spread through the air with no sexual contact involved at all.
How Chlamydia Spreads Sexually
The vast majority of C. trachomatis infections are transmitted through vaginal, anal, or oral sex. This is the route that public health campaigns focus on because it accounts for nearly all cases in adults. You can get chlamydia in the genitals, rectum, or throat depending on the type of sexual contact. Ejaculation does not need to occur for transmission to happen.
You cannot catch chlamydia from kissing, hugging, sitting on toilet seats, sharing cups or cutlery, or from swimming pools and baths. Casual, non-intimate contact poses no risk.
Mother-to-Baby Transmission During Birth
A pregnant person with a chlamydia infection of the cervix can pass the bacterium to their baby as the infant moves through the birth canal. This can cause eye infections (neonatal conjunctivitis) or pneumonia in the newborn. This is why routine chlamydia screening is part of standard prenatal care. Treatment before delivery eliminates the risk to the baby.
Auto-Inoculation: Spreading It to Yourself
If you have a genital chlamydia infection, you can transfer the bacteria to other parts of your own body through touch. The most common example is genital-to-eye transmission. Touching infected genital fluids and then rubbing your eyes can cause chlamydial conjunctivitis, a painful eye infection. The CDC notes that chlamydia can also spread from the vagina to the rectum (or vice versa) without anal sex, simply through direct contact between infected sites.
This type of self-transfer is called auto-inoculation. It’s preventable with basic hand hygiene, particularly washing your hands after touching your genitals.
Trachoma: An Eye Infection Spread Without Sex
The same species of bacterium, C. trachomatis, causes trachoma, a chronic eye infection that has nothing to do with sexual contact. Trachoma spreads through direct personal contact with eye or nose discharge from an infected person, through shared clothes and bedding, and through flies that land on the faces of infected individuals. Young children are the main reservoir of infection.
Trachoma is caused by different strains of C. trachomatis than those involved in genital infections, and it remains a significant public health problem in parts of Africa, Asia, and the Middle East. According to the World Health Organization, it is the leading infectious cause of blindness worldwide. The strains involved are well adapted to non-sexual spread: research published in PLOS Neglected Tropical Diseases found that viable chlamydia DNA could be recovered from plastic, cotton cloth, and skin surfaces for up to 24 hours, supporting the idea that contaminated fabrics and household surfaces play a real role in transmission.
Other Chlamydia Species That Aren’t Sexual at All
When most people say “chlamydia,” they mean C. trachomatis. But the chlamydia family includes other species with completely different transmission routes.
- Chlamydia pneumoniae spreads through respiratory droplets, the same way a cold does. It causes lung infections and bronchitis and has no connection to sexual activity.
- Chlamydia psittaci is a zoonotic infection transmitted by birds. Parrots, cockatiels, parakeets, pigeons, chickens, and turkeys can all carry it. Humans get infected by inhaling aerosolized bacteria from bird droppings or secretions. Pet shop employees and poultry workers face the highest risk, though 25 to 50 percent of people diagnosed with this infection deny any known bird contact.
Neither of these species is sexually transmitted. They cause respiratory illness, not genital infections.
Why the Confusion Exists
The confusion is understandable. “Chlamydia” in everyday conversation almost always refers to the genital STI, which is the most common bacterial sexually transmitted infection worldwide. Because it’s so strongly associated with sexual activity, many people assume sex is the only possible route. For the genital strains in adults, sexual contact is overwhelmingly the primary pathway. But the bacterium itself is more versatile than its reputation suggests.
If you’re an adult with a genital or rectal chlamydia infection and you haven’t had sexual contact, the most likely explanations are auto-inoculation from another infected site, transmission during birth (for eye or respiratory infections in newborns), or, rarely, contact with infected genital fluids through non-penetrative intimate activity. Transmission from surfaces like toilet seats or shared towels is not considered a realistic route for genital chlamydia, even though the ocular strains involved in trachoma can survive on fabrics for hours.