Sexually Transmitted Disease
Sexually transmitted disease (STD), also known as a sexually transmitted infection (STI) or venereal disease (VD), is an illness that has 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.
Until the 1990s, STDs were commonly known as venereal diseases: Veneris is the Latin genitive form of the name Venus, the Roman goddess of love. Social disease was another euphemism.
Sexually transmitted infection is a broader term than sexually transmitted disease. An infection is a colonization by a parasitic species, which may not cause any adverse effects. In a disease the infection leads to impaired or abnormal function. In either case the condition may not exhibit signs or symptoms. Increased understanding of infections like HPV, which infects most sexually active individuals but cause disease in only a few has led to increased use of the term STI. Public health officials originally introduced the term sexually transmitted infection, which clinicians are increasingly using alongside the term sexually transmitted disease in order to distinguish it from the former.
STD may refer only to infections that are causing diseases, or it may be used more loosely as a synonym for STI. Because most of the time people do not know that they are infected with an STD until they are tested or start showing symptoms of disease, most people use the term STD, even though the term STI is also appropriate in many cases.
Moreover, the term sexually transmissible disease is sometimes used since it is less restrictive in consideration of other factors or means of transmission. For instance, meningitis is transmissible by means of sexual contact but is not labeled as an STI because sexual contact is not the primary vector for the pathogens that cause meningitis. This discrepancy is addressed by the probability of infection by means other than sexual contact. In general, an STI is an infection that has a negligible probability of transmission by means other than sexual contact, but has a realistic means of transmission by sexual contact (more sophisticated means—blood transfusion, sharing of hypodermic needles—are not taken into account). Thus, one may presume that, if a person is infected with an STI, e.g., chlamydia, gonorrhea, genital herpes, it was transmitted to him/her by means of sexual contact.
The diseases on this list are most commonly transmitted solely by sexual activity. Many infectious diseases, including the common cold, influenza, pneumonia, and most others that are transmitted person-to-person can also be transmitted during sexual contact, if one person is infected, due to the close contact involved. However, even though these diseases may be transmitted during sex, they are not considered STDs.
* Chancroid (Haemophilus ducreyi)
* Chlamydia (Chlamydia trachomatis)
* Granuloma inguinale or (Klebsiella granulomatis)
* Gonorrhea (Neisseria gonorrhoeae)
* Syphilis (Treponema pallidum)
* Candidiasis (yeast infection)
Micrograph showing the viral cytopathic effect of herpes (ground glass nuclear inclusions, multi-nucleation). Pap test. Pap stain.
* 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, and the route of transmission of Hepatitis D (only if infected with B) is uncertain, but may include sexual transmission.)
* 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
* Crab louse, colloquially known as "crabs" or "pubic lice" (Pthirus pubis)
* Scabies (Sarcoptes scabiei)
* Trichomoniasis (Trichomonas vaginalis)
The risks and transmission probabilities of sexually transmitted diseases are summarized by act in the table below.
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