Chlamydia is one of the most common sexually transmitted infections (STIs) globally, caused by the bacterium Chlamydia trachomatis. The infection affects both men and women and is easily treated with antibiotics, but if left undiagnosed, it can lead to serious, permanent reproductive damage. A common misconception is that the risk of contracting Chlamydia is only present with multiple sexual partners. However, it is entirely possible to contract this infection even in a mutually exclusive relationship with only one partner. The risk is determined by the presence of the infection in any one partner, not the number of partners.
How Chlamydia Spreads
Chlamydia is transmitted through the exchange of bodily fluids during sexual contact, including vaginal, anal, and oral sex. The bacteria are present in semen, pre-ejaculate, and vaginal fluids, allowing for transmission between partners. The infection occurs when these fluids come into contact with the mucous membranes of the genitals, rectum, or throat.
Transmission of the Chlamydia trachomatis bacterium does not require full penetration or ejaculation. Any intimate sexual contact involving the transfer of infected genital secretions carries the risk of spreading the infection. The infection can be passed on in a single sexual encounter. The risk is tied solely to the presence of the bacteria in a partner.
The Hidden Factor of Asymptomatic Infection
The primary reason Chlamydia can appear unexpectedly within a seemingly low-risk, one-partner relationship is its often silent nature. Chlamydia is frequently called a “silent infection” because the majority of people who have it experience no noticeable symptoms. Approximately 75% of infections in women and about 50% of infections in men are initially asymptomatic.
This lack of symptoms allows an infection to be carried unknowingly for an extended period, sometimes for over a year, without the host realizing they are infected. A partner who acquired Chlamydia from a previous relationship may have been carrying the bacteria for months or years without any sign of illness. They then transmit the infection to their current partner, who may also remain asymptomatic.
The incubation period can range from a few days to several weeks, but many people never develop noticeable symptoms at all. This extended, asymptomatic duration means the infection can be passed along without anyone being aware of the chain of transmission. Contracting Chlamydia from a monogamous partner does not necessarily indicate recent infidelity, but rather that one partner unknowingly brought a long-standing infection into the relationship from their past.
Why Regular Screening is Necessary
Given the high rate of symptomless carriage, regular screening is the most effective strategy to detect and treat Chlamydia before it causes complications. Annual Chlamydia screening is recommended for all sexually active women aged 24 and younger. Screening is also advised for women aged 25 and older who have risk factors, such as a new sexual partner or multiple partners.
Testing for Chlamydia is typically simple, often involving a urine sample or a swab, and results are generally available quickly. While there is insufficient evidence to recommend routine screening for all sexually active young men, it should be considered in clinical settings with a high prevalence of the infection. Men who have sex with men should also be screened annually at sites of contact, such as the urethra and rectum.
If a positive result is found, Chlamydia is easily cured with a course of antibiotics. Both partners in a relationship must be tested and treated simultaneously to prevent re-infection. Prompt diagnosis and treatment are the only ways to interrupt the transmission cycle and protect long-term reproductive health.