also referred to as sexually transmitted infections (STI) and venereal diseases (VD), are illnesses that have a significant probability of transmission between humans by means of human sexual behavior, including vaginal intercourse, oral sex, and anal sex. While in the past, these illnesses have mostly been referred to as STDs or VD, in recent years the term sexually transmitted infections (STIs) has been preferred, as it has a broader range of meaning; a person may be infected, and may potentially infect others, without having a disease. Some STIs can also be transmitted via the use of IV drug needles after its use by an infected person, as well as through childbirth or breastfeeding. Sexually transmitted infections have been well known for hundreds of years, and venereology is the branch of medicine that studies these diseases.

Bacterial

• Chancroid (Haemophilus ducreyi)
• Chlamydia (Chlamydia trachomatis)
• Gonorrhea (Neisseria gonorrhoeae), colloquially known as „the clap“
• Granuloma inguinale or (Klebsiella granulomatis)
• Syphilis (Treponema pallidum)

Fungal

• Candidiasis (yeast infection)

Viral

• Viral hepatitis (Hepatitis B virus)—saliva, venereal fluids.
  (Note: Hepatitis A and Hepatitis E are transmitted via the fecal-oral route; Hepatitis C is rarely sexually transmittable,^[4] and the route of transmission of Hepatitis D (only if infected with B) is uncertain, but may include sexual transmission.^[5][6][7])
• Herpes simplex (Herpes simplex virus 1, 2) skin and mucosal, transmissible with or without visible blisters
• HIV (Human Immunodeficiency Virus)—venereal fluids, semen, breast milk, blood
• HPV (Human Papillomavirus)—skin and mucosal contact. ‚High risk‘ types of HPV cause almost all cervical cancers, as well as some anal, penile, and vulvar cancer. Some other types of HPV cause genital warts.
• Molluscum contagiosum (molluscum contagiosum virus MCV)—close contact

Parasites

• Crab louse, colloquially known as „crabs“ or „pubic lice“ (Pthirus pubis)
• Scabies (Sarcoptes scabiei)

Protozoal

• Trichomoniasis (Trichomonas vaginalis), colloquially known as „trich“

Source: Wikipedia