In the United States alone, roughly 20 million new sexually transmitted infections occur every year, and more than 2.2 million cases of chlamydia, gonorrhea, and syphilis were officially reported in 2024. Globally, the World Health Organization estimates 374 million new infections of the four most common curable STIs each year, which works out to over one million new cases per day. These numbers represent new infections, not the total number of people currently living with an STI, which is significantly higher once you include chronic and often-undiagnosed infections like herpes and HIV.
STI Cases Reported in the US Each Year
The CDC tracks three bacterial STIs through mandatory reporting: chlamydia, gonorrhea, and syphilis. In 2024, the combined total across these three infections was 2,249,636 reported cases. Chlamydia accounted for the largest share at nearly 1.52 million cases, followed by gonorrhea at about 543,000 and syphilis at roughly 190,000. Congenital syphilis, which passes from a pregnant person to their baby, accounted for 3,941 of those syphilis cases.
These numbers actually represent a 9% decline from 2023, marking the third consecutive year of decreases. Still, 2.2 million is a floor, not a ceiling. Many infections go undiagnosed and unreported, so the true number of new cases each year is estimated to be closer to 20 million when you include infections like herpes, HPV, and trichomoniasis that aren’t tracked through mandatory reporting.
How Many People Live With Chronic STIs
Some STIs clear with treatment or on their own, but others stay in the body for life. About 12% of Americans aged 14 to 49 have genital herpes (HSV-2), based on national survey data. That translates to tens of millions of people carrying the virus at any given time, most of whom have mild or no symptoms and may not know they’re infected.
An estimated 1.2 million people in the US aged 13 and older are living with HIV. About 13% of them, roughly 158,000 people, don’t know their status because they haven’t been tested. HPV is even more widespread. Most sexually active people will contract at least one strain of HPV at some point, though the immune system clears most infections within a year or two.
Young Adults Carry a Disproportionate Share
People aged 15 to 24 make up just over 25% of the sexually active population but account for about half of all new STI cases each year. That concentration is driven by a mix of biological and behavioral factors: younger people are less likely to use barrier protection consistently, less likely to have been screened recently, and in the case of young women, may have cervical tissue that is more susceptible to certain infections.
The financial toll reflects this disparity. New STIs acquired in a single year impose an estimated $15.9 billion in lifetime direct medical costs. Infections among 15-to-24-year-olds account for $4.2 billion of that total, about 26%. Sexually acquired HIV drives the bulk of the overall cost at $13.7 billion, largely because it requires lifelong treatment.
Global Numbers
The World Health Organization estimates that 374 million new infections of the four most common curable STIs (chlamydia, gonorrhea, syphilis, and trichomoniasis) occurred worldwide in 2020 among adults aged 15 to 49. That pace of over a million new infections per day doesn’t include viral STIs like herpes, HIV, or HPV, which would push the total considerably higher. Access to testing and treatment varies enormously by country, so in many regions the true burden is likely underestimated.
Why the Real Numbers Are Higher Than Reports Suggest
A major reason STI statistics undercount reality is that most infections cause no obvious symptoms. Research on chlamydia finds that roughly 61% of infections in women produce no symptoms at all. For gonorrhea, the figure is about 53%, and for trichomoniasis, around 57%. People without symptoms rarely seek testing, so their infections go uncounted in surveillance data and can be unknowingly passed to partners.
Screening gaps compound the problem. Many people don’t get tested regularly, either because they assume they’d notice symptoms, because they lack access to affordable healthcare, or because stigma keeps them from asking. The CDC recommends annual chlamydia and gonorrhea screening for all sexually active women under 25 and for anyone with new or multiple partners, but adherence to those guidelines remains inconsistent. The gap between reported cases and estimated true infections is why public health agencies treat surveillance numbers as a significant undercount rather than a complete picture.
What These Numbers Mean in Practical Terms
If you’re sexually active, STIs are not rare or unusual. They’re one of the most common categories of infectious disease. Having one doesn’t signal anything about character or hygiene. It signals that you’re part of a population where these infections circulate widely, often invisibly. The most common bacterial STIs (chlamydia, gonorrhea, syphilis) are fully curable with antibiotics when caught early. Viral infections like herpes and HIV aren’t curable but are highly manageable with modern treatment, and in the case of HIV, treatment can reduce the virus to undetectable and untransmittable levels.
Regular screening is the single most effective way to catch infections early, particularly given how often they cause no symptoms. If you haven’t been tested recently and are sexually active, a simple panel covering the most common infections is widely available through primary care offices, sexual health clinics, and at-home testing kits.