The most common STD overall is HPV (human papillomavirus). About 85% of sexually active people will get an HPV infection at some point in their lives, and an estimated 300 million women worldwide are living with one at any given time. But the answer shifts depending on whether you’re talking about viral or bacterial infections, and whether you’re counting new cases per year or total people currently infected. Here’s how the numbers actually break down.
HPV Is the Most Common STD Overall
HPV stands apart from every other sexually transmitted infection by sheer scale. It’s so widespread that getting it is essentially the norm for sexually active adults, not the exception. Most people clear the virus on their own within a year or two without ever knowing they had it. A small percentage of infections, however, persist and can lead to genital warts or, over many years, cancers of the cervix, throat, anus, or penis.
Vaccination has dramatically reduced HPV rates in countries with strong immunization programs, but the virus remains the single most prevalent STD on the planet. If you’re sexually active and weren’t vaccinated before your first sexual contact, the odds are high that you’ve already been exposed.
The Most Common STDs by Category
The picture changes when you separate viral infections from bacterial ones, and when you look at how many new cases occur each year versus how many people are living with an infection right now.
By Total Prevalence (People Currently Infected)
When you count everyone living with an infection worldwide, viral STDs dominate the list:
- HPV: 300 million women infected (male figures are harder to estimate but comparable)
- Genital herpes: more than 520 million people
- Hepatitis B: 254 million people with chronic infection
These numbers are so large because viral STDs tend to stick around. Herpes and hepatitis B are lifelong infections, and HPV can persist for months or years before the immune system clears it.
By New Cases Per Year
If you’re asking which STD spreads the fastest right now, the World Health Organization estimated 374 million new infections in 2020 across four curable STDs alone:
- Trichomoniasis: 156 million new cases
- Chlamydia: 129 million new cases
- Gonorrhea: 82 million new cases
- Syphilis: 7.1 million new cases
Trichomoniasis topping this list surprises most people. It’s caused by a parasite, not a bacterium or virus, and it rarely makes headlines. Yet it infects more people each year than chlamydia and gonorrhea, partly because it often causes no symptoms and goes undetected for long stretches.
Chlamydia Is the Most Reported STD in the U.S.
In the United States, chlamydia consistently leads the list of reported bacterial STDs by a wide margin. Provisional CDC data for 2024 recorded roughly 1.5 million chlamydia cases, followed by about 543,000 gonorrhea cases and 190,000 syphilis cases. Combined, that’s more than 2.2 million reported infections in a single year, and the true number is certainly higher because many cases are never diagnosed.
The good news: reported STI totals in the U.S. dropped 9% from 2023 to 2024, marking the third consecutive year of decline.
Why So Many Cases Go Undetected
The reason these infections spread so efficiently is that most people who have them don’t feel sick. CDC estimates show that about 84% of men and 75% of women with chlamydia have no symptoms at all. Gonorrhea is similar: roughly 41% of infected men and 68% of infected women are completely asymptomatic.
This creates an obvious problem. People who feel fine don’t get tested, and they unknowingly pass the infection to partners. By the time symptoms do appear, if they ever do, the infection may have been present for weeks or months. For chlamydia in particular, untreated infection in women can lead to pelvic inflammatory disease, chronic pelvic pain, and, in serious cases, infertility or ectopic pregnancy.
Who Should Get Screened and How Often
Because so many infections are silent, screening is the only reliable way to catch them early. Current CDC guidelines recommend annual chlamydia and gonorrhea testing for all sexually active women under 25 and for women 25 and older who have risk factors like new or multiple partners. Men who have sex with men should be tested at least once a year, and every three to six months if they have multiple partners or are on PrEP.
There’s no routine screening recommendation for low-risk heterosexual men, largely because the evidence hasn’t shown it reduces transmission at the population level. That said, any man with symptoms like painful urination or unusual discharge should get tested promptly.
For HPV, there’s no standard screening test for men. Women are screened through cervical cancer screening (Pap tests and HPV tests), typically starting at age 21 or 25 depending on the guidelines used. Vaccination remains the most effective prevention tool, ideally given before a person becomes sexually active.
How These Infections Are Treated
Bacterial and parasitic STDs are curable. Chlamydia, gonorrhea, syphilis, and trichomoniasis can all be cleared with antibiotics or antiparasitic medication, often with a single dose or a short course. Partners need to be treated at the same time to prevent reinfection, which is one of the most common reasons people test positive again after treatment.
Viral STDs are a different story. There’s no cure for herpes or HPV, though both are manageable. Herpes outbreaks can be controlled with antiviral medication, and most HPV infections resolve on their own. Hepatitis B can become a chronic condition requiring long-term management, but a vaccine prevents it entirely.
The practical takeaway is straightforward. The most common STDs are also the most treatable or preventable, but only if they’re caught. Since the majority produce no symptoms, regular screening based on your age, sex, and sexual activity is the single most effective thing you can do to protect yourself and your partners.