Quick Answer

There are roughly 30 organisms that can be sexually transmitted. The most common are: chlamydia, gonorrhea, syphilis, HIV, herpes simplex (HSV-1 and HSV-2), HPV, trichomoniasis, hepatitis A, B, and C, bacterial vaginosis (not strictly an STI), yeast infections (not STI), mycoplasma genitalium, ureaplasma, PID, epididymitis, scabies, pubic lice, molluscum contagiosum, mpox, and lymphogranuloma venereum (an aggressive chlamydia strain).

  • Bacterial group: chlamydia, gonorrhea, syphilis, mycoplasma genitalium, LGV (chlamydia variant).
  • Viral group: HIV, herpes (HSV-1/2), HPV, hepatitis A/B/C, molluscum, mpox.
  • Parasitic: trichomoniasis, pubic lice, scabies.
  • Emerging/contested: M. genitalium, ureaplasma, BV (dysbiosis, not infection).

Context Most Pages Skip

Not all are 'infections' in the classic sense — BV is a microbial imbalance, yeast is normal flora overgrowing, and epididymitis is inflammation with multiple causes. The list expands as research identifies new organisms and contracts as some prove non-transmissible.

How many is 'common'?

Roughly 8-10 infections account for 95%+ of diagnosed STIs: chlamydia, gonorrhea, syphilis, HIV, herpes, HPV, trichomoniasis, and hepatitis B. The rest are far less common.

Total number

The CDC tracks ~20 sexually transmitted conditions; adding rare infections pushes the number to ~30, but most people will only encounter the top 6-8 in their lifetime.

⚕️ This page is educational and does not replace advice from a licensed clinician. If you may have been exposed to an STI, get tested — most infections are manageable, and many are fully curable.

Sources & Further Reading

Figures reflect CDC surveillance and WHO estimates; they are population statistics, not personal risk predictions.