Short answer
America’s commonest STIs, in roughly descending frequency: HPV (tens of millions of prevalent infections. The commonest by far), chlamydia (millions of yearly cases, mostly silent), trichomoniasis (millions, under-screened), gonorrhea (hundreds of thousands reported, resistance-watched), genital herpes (roughly 1 in 6 adults for HSV-2 alone, plus genital HSV-1), syphilis (rising across stages, including congenital), HIV, and hepatitis B.
Youth bears the heaviest burden; silence is the shared trait; screening, not symptoms, finds nearly all of them.
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See Tests & Prices →The ranking. Scale plus character
- HPV: most sexually active people contract it, usually harmlessly and silently. Vaccination and screening manage the minority that progresses.
- Chlamydia: the leading reportable bacterial STI, majority-silent, infertility-relevant when untreated.
- Trichomoniasis: widespread and under-tested (many panels omit it without specific ordering).
- Gonorrhea: resistance surveillance’s highest-priority bacterial STI.
- Genital herpes: lifelong manageable infection with shedding-aware precautions.
- Syphilis: resurgent across stages with congenital cases as the systems-failure signal.
- HIV and hepatitis B: lower incidence, higher per-case stakes, both manageable into normal life with treatment.
Population-data literacy for reading these numbers: Understanding US STI Surveillance Statistics.
Who is most affected. Burden concentrates
- Ages 15–24 account for about half of new infections (biology, networks, access gaps. Not character).
- MSM face concentrated HIV, syphilis, and gonorrhea epidemics (multi-site screening norms respond to this concentration).
- Racial disparities reflect access gaps and network effects, never behavior alone.
- Congenital syphilis tracks missed maternal screening visit by visit. Each case a cascade of missed opportunities, each preventable.
What commonness implies for you. Action, not alarm
- Screen for the common ones on schedule (chlamydia/gonorrhea NAAT yearly when sexually active and young, cervical screening per age schedule, HIV baseline plus repeats by risk).
- Vaccinate against HPV and hepatitis B (the two preventable common STIs. Completed series, not intentions).
- Treat “everyone has it” as a testing argument, never a reassurance (commonness raises your pre-test probability. It never lowers the stakes, since infertility, cancer, and congenital harm concentrate in untreated common infections).
When to seek care
Per the screening schedules for your age and risk. Common infections are found by routine testing, not by symptoms.