The number of STIs (sexually transmitted infections) will vary depending on what is counted as an STI and whether sexually transmissible infections are counted. The Medical Institute uses a list of STIs that is adapted from chapter headings in a standard STI textbook¹. This list, which appears below in alphabetical order, has 27 different infections.

Bacterial:
1. bacterial vaginosis
2. chancroid
3. chlamydia
4. donovanosis
5. gonorrhea
6. lymphogranuloma venereum
7. mycoplasma, genital
8. syphilis
9. treponematosis, endemic

Ectoparasitic:
10. lice, pubic
11. scabies
12. candidiasis, vulvovaginal

Protozoal:
13. amebiasis
14. cryptosporidium
15. giardiasis
16. trichomoniasis

Viral:
17. cytomegalovirus
18. Epstein Barr virus
19. hepatitis A
20. hepatitis B
21. hepatitis C
22. hepaptitis D
23. herpes simplex virus (HSV-1 and HSV-2)
24. human immunodeficiency virus (HIV)
25. human papillomavirus (HPV)
26. human T-cell lymphotropic virus (HTLV-1)
27. molluscum contagiosum

Reviewed by: Jennifer A. Shuford, MD, MPH
Date: October 2008

Reference:
1. Holmes KK, Sparling PF, Stamm WE, et al. Sexually Transmitted Diseases, 4th Ed. New York, NY: McGraw Hill Medical; 2008.