Chlamydia is the most commonly reported bacterial sexually transmitted infection in the United States, with over 1.5 million cases reported in 2024 alone. The true number is almost certainly higher, because the majority of people who have it never develop symptoms and never get tested.
How Many People Get Chlamydia Each Year
In 2024, the CDC recorded 1,515,985 reported chlamydia cases in the U.S. That number only reflects people who were actually tested and diagnosed. Since 75% of women and 50% of men with chlamydia experience no symptoms at all, a large portion of infections go completely undetected. Previous CDC estimates have suggested the actual number of new chlamydia infections per year in the U.S. is closer to 4 million when undiagnosed cases are included.
Globally, chlamydia is part of a massive burden of curable STIs. The World Health Organization estimated that chlamydia, gonorrhea, syphilis, and trichomoniasis together caused 374 million new infections worldwide in 2020, averaging over 1 million new cases per day among adults aged 15 to 49. Chlamydia accounts for a significant share of that total.
Who Gets It Most Often
Young adults carry a disproportionate share of chlamydia infections. People between the ages of 15 and 24 consistently account for the highest rates of reported cases, which is why screening guidelines focus heavily on this age group. Sexual activity, having new or multiple partners, and inconsistent condom use all increase exposure risk, and these patterns tend to be more common among younger people.
Reported rates are significantly higher in women than in men, but that gap is misleading. Women are screened far more often because routine chlamydia screening is a standard part of preventive care for sexually active women under 25. The U.S. Preventive Services Task Force recommends annual screening for all sexually active women aged 24 and younger, and for older women with risk factors like new partners. For men, the task force has said there isn’t enough evidence yet to recommend routine screening. So men are typically only tested when they have symptoms or know they’ve been exposed, meaning many male infections simply go uncounted.
Why So Many Cases Go Undiagnosed
The single biggest reason chlamydia is so common is that most people who have it don’t know. Three out of four women and half of men with chlamydia have zero symptoms. No pain, no discharge, no obvious sign anything is wrong. Without symptoms, there’s no reason to seek testing unless it’s part of a routine screening.
This creates a cycle. People who don’t know they’re infected continue having sex and can pass chlamydia to partners without realizing it. Those partners may also remain asymptomatic, and the chain continues. When symptoms do appear, they typically show up one to three weeks after exposure and can include unusual discharge, burning during urination, or, in women, bleeding between periods. But waiting for symptoms is an unreliable strategy for catching this infection.
Reinfection Is Surprisingly Common
Even after successful treatment, getting chlamydia again is not unusual. Among teenagers treated for chlamydia, about 6% tested positive for a new infection within six months, 11% within one year, and 17% within two years. Chlamydia treatment doesn’t give you any lasting immunity. If you’re exposed again, you can be infected again just as easily as the first time.
This is why retesting three months after treatment is recommended. Partners also need to be treated at the same time. If only one person in a sexual partnership takes antibiotics, the untreated partner can simply pass the infection right back.
Your Actual Risk Depends on a Few Factors
The population-level numbers are striking, but your individual risk depends on specifics. The factors that matter most are your age (under 25 carries higher risk), whether you have new or multiple sexual partners, whether condoms are used consistently, and whether your partners have been tested recently.
If you’re a sexually active woman under 25, routine annual screening is the standard recommendation regardless of symptoms or perceived risk. Women 25 and older should be screened if they have new partners or other risk factors. For men, there’s no universal screening guideline, but testing makes sense if you have a new partner, multiple partners, or any symptoms.
Chlamydia is easily treated with a short course of antibiotics, and when caught early, it rarely causes lasting problems. Left untreated, it can lead to pelvic inflammatory disease in women (which can affect fertility), and in men it can cause painful inflammation of the reproductive tract. The infection itself is common enough that there’s no reason to feel singled out by a positive result. Getting tested regularly and treating it promptly is what actually matters.