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Istituto Superiore di Sanità
EpiCentro - Epidemiology for public health
Epidemiology for public health - ISS

Sexually transmitted infections (STIs) include several infectious diseases that are extremely common worldwide. They can cause acute symptoms, chronic infections and severe long-term complications in millions of people each year, and their treatment requires extensive financial resources.


What STIs are there?

As reported by the WHO, over 30 different pathogens (including bacteria, viruses, protozoa and parasites) are currently known to be responsible for STIs.


Main STIs caused by bacteria

  • Chlamydia infection (Chlamydia trachomatis, including serovars L1, L2, L3, which are responsible for lymphogranuloma venereum)
  • Gonorrhoea (Neisseria gonorrhoeae)
  • Syphilis (Treponema pallidum)
  • Venereal ulcer or chancroid (Haemophilus ducreyi)
  • Donovanosis or granuloma inguinale (Klebsiella granulomatis)
  • Non-gonococcal and non-chlamydial bacterial infections (Gardnerella vaginalisMycoplasma genitaliumMycoplasma hominisUreaplasma urealyticumGroup B Streptococcus).

Main STIs caused by viruses

Main STIs caused by protozoa

  • Trichomonas infection (Trichomonas vaginalis

Main STIs caused by parasites

  • Pediculosis pubis (Phthirus pubis)
  • Scabies (Sarcoptes scabiei)

Publication date: 28 January 2021