Sexually transmitted disease

A sexually transmitted disease (STD), also known as sexually transmitted infection (STI) or venereal disease (VD), is an illness that has a significant probability of transmission between humans or animals by means of sexual contact, 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 infection (STI) has been preferred, as it has a broader range of meaning; a person may be infected, and may potentially infect others, without showing signs of disease. Some STIs can also be transmitted via use of an IV drug needle 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.

Classification and terminology

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.

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. According to the Ethiopian Aids Resource Center FAQ, "Sometimes the terms STI and STD are used interchangeably. This can be confusing and not always accurate, so it helps first to understand the difference between infection and disease. Infection simply means that a germ — virus, bacteria, or parasite — that can cause disease or sickness is present inside a person’s body. An infected person does not necessarily have any symptoms or signs that the virus or bacteria is actually hurting his or her body; they do not necessarily feel sick. A disease means that the infection is actually causing the infected person to feel sick, or to notice something is wrong. For this reason, the term STI — which refers to infection with any germ that can cause an STD, even if the infected person has no symptoms — is a much broader term than STD."

Specifically, the term STD refers only to infections that are causing symptoms. Because most of the time people do not know that they are infected with an STD until they start showing symptoms of disease, most people use the term STD, even though the term STI is also appropriate in many cases.

Pathology

Many STDs are (more easily) transmitted through the mucous membranes of the penis, vulva, rectum, urinary tract and (less often - depending on type of infection)[citation needed] the mouth, throat, respiratory tract and eyes. The visible membrane covering the head of the penis is a mucous membrane, though it produces no mucus (similar to the lips of the mouth). Mucous membranes differ from skin in that they allow certain pathogens into the body. Pathogens are also able to pass through breaks or abrasions of the skin, even minute ones. The shaft of the penis is particularly susceptible due to the friction caused during penetrative sex. The primary sources of infection in ascending order are venereal fluids, saliva, mucosal or skin (particularly the penis), infections may also be transmitted from feces, urine and sweat.The amount required to cause infection varies with each pathogen but is always less than you can see with the naked eye.

This is one reason that the probability of transmitting many infections is far higher from sex than by more casual means of transmission, such as non-sexual contact—touching, hugging, shaking hands—but it is not the only reason. Although mucous membranes exist in the mouth as in the genitals, many STIs seem to be easier to transmit through oral sex than through deep kissing. According to a safe sex chart, many infections that are easily transmitted from the mouth to the genitals or from the genitals to the mouth, are much harder to transmit from one mouth to another.[4] With HIV, genital fluids happen to contain much more of the pathogen than saliva. Some infections labeled as STIs can be transmitted by direct skin contact. Herpes simplex and HPV are both examples. KSHV, on the other hand, may be transmitted by deep-kissing but also when saliva is used as a sexual lubricant.

Depending on the STD, a person may still be able to spread the infection if no signs of disease are present. For example, a person is much more likely to spread herpes infection when blisters are present (STD) than when they are absent (STI). However, a person can spread HIV infection (STI) at any time, even if he/she has not developed symptoms of AIDS (STD).

All sexual behaviors that involve contact with the bodily fluids of another person should be considered to contain some risk of transmission of sexually transmitted diseases. Most attention has focused on controlling HIV, which causes AIDS, but each STD presents a different situation.

As may be noted from the name, sexually transmitted diseases are transmitted from one person to another by certain sexual activities rather than being actually caused by those sexual activities. Bacteria, fungi, protozoa or viruses are still the causative agents. It is not possible to catch any sexually transmitted disease from a sexual activity with a person who is not carrying a disease; conversely, a person who has an STD got it from contact (sexual or otherwise) with someone who had it, or his/her bodily fluids. Some STDs such as HIV can be transmitted from mother to child either during pregnancy or breastfeeding.

Although the likelihood of transmitting various diseases by various sexual activities varies a great deal, in general, all sexual activities between two (or more) people should be considered as being a two-way route for the transmission of STDs, i.e., "giving" or "receiving" are both risky although receiving carries a higher risk.

Healthcare professionals suggest safer sex, such as the use of condoms, as the most reliable way of decreasing the risk of contracting sexually transmitted diseases during sexual activity, but safer sex should by no means be considered an absolute safeguard. The transfer of and exposure to bodily fluids, such as blood transfusions and other blood products, sharing injection needles, needle-stick injuries (when medical staff are inadvertently jabbed or pricked with needles during medical procedures), sharing tattoo needles, and childbirth are other avenues of transmission. These different means put certain groups, such as medical workers, and haemophiliacs and drug users, particularly at risk.

It is possible to be an asymptomatic carrier of sexually transmitted diseases. In particular, sexually transmitted diseases in women often cause the serious condition of pelvic inflammatory disease.

Prevalence

STD incidence rates remain high in most of the world, despite diagnostic and therapeutic advances that can rapidly render patients with many STDs noninfectious and cure most. In many cultures, changing sexual morals and oral contraceptive use have eliminated traditional sexual restraints, especially for women, and both physicians and patients have difficulty dealing openly and candidly with sexual issues. Additionally, development and spread of drug-resistant bacteria (e.g., penicillin-resistant gonococci) makes some STDs harder to cure. The effect of travel is most dramatically illustrated by the rapid spread of the AIDS virus (HIV-1) from Africa to Europe and the Americas in the late 1970s.

Commonly reported prevalences of STIs among sexually active adolescent girls both with and without lower genital tract symptoms include chlamydia trachomatis (10 to 25%), Neisseria gonorrhoeae (3 to 18%), syphilis (0 to 3%), Trichomonas vaginalis (8 to 16%), and herpes simplex virus (2 to 12%).Among adolescent boys with no symptoms of urethritis, isolation rates include C. trachomatis (9 to 11%) and N. gonorrhoeae (2 to 3%).

In 1996, WHO estimated that more than 1 million people were being infected daily. About 60% of these infections occur in young people <25 years of age, and of these 30% are <20 years. Between the ages of 14 and 19, STDs occur more frequently in girls than boys by a ratio of nearly 2:1; this equalizes by age 20. An estimated 340 million new cases of syphilis, gonorrhea, chlamydia and trichomoniasis occurred throughout the world in 1999.

Prevention
Main article: Safe sex

Prevention is key in addressing incurable STIs, such as HIV & herpes.

Vaccines are available that protect against some viral STIs, such as Hepatitis B and some types of HPV. Vaccination before initiation of sexual contact is advised to assure maximal protection.

The most effective way to prevent sexual transmission of STIs is to avoid contact of body parts or fluids which can lead to transfer, not necessarily any sexual activity with an infected partner. No contact minimizes risk. Proper use of condoms (male or female) reduces contact and risk.

Ideally, both partners should get tested for STIs before initiating sexual contact, or before resuming contact if a partner engaged in contact with someone else. Many infections are not detectable immediately after exposure, so enough time must be allowed between possible exposures and testing for the tests to be accurate. Certain STIs, particularly certain persistent viruses like HPV, may be impossible to detect with current medical procedures.

Many diseases that establish permanent infections can so occupy the immune system that other diseases become more easily transmitted. The innate immune system led by defensins against HIV can prevent transmission of HIV when viral counts are very low, but if busy with other viruses or overwhelmed, HIV can establish itself. Certain viral STI's also greatly increase the risk of death for HIV infected patients.

Condoms

Condoms only provide protection when used properly as a barrier, and only to and from the area that it covers. Uncovered areas are still susceptible to many STDs. In the case of HIV, sexual transmission routes almost always involve the penis, as HIV cannot spread through unbroken skin, thus properly shielding the insertive penis with a properly worn condom from the vagina and anus effectively stops HIV transmission. Other STDs, even viral infections, can be prevented with the use of latex condoms as a barrier. Some microorganisms and viruses are small enough to pass through the pores in natural skin condoms, but are still too large to pass through latex condoms.

Condoms are designed, tested, and manufactured to never fail if used properly. There has not been one documented case of an HIV transmission due to an improperly manufactured condom

Proper usage entails:

* Not putting the condom on too tight at the end, and leaving 1.5 cm (3/4 inch) room at the tip for ejaculation. Putting the condom on snug can and often does lead to failure.
* Wearing a condom too loose can defeat the barrier.
* Avoiding inverting, spilling a condom once worn, whether it has ejaculate in it or not, even for a second.
* Avoiding condoms made of substances other than latex or polyurethane, as they don't protect against HIV.
* Avoiding the use of oil based lubricants (or anything with oil in it) with latex condoms, as oil can eat holes into them.
* Using flavored condoms for oral sex only, as the sugar in the flavoring can lead to yeast infections if used to penetrate.

Not following the first five guidelines above perpetuates the common misconception that condoms aren't tested or designed properly.

In order to best protect oneself and the partner from STIs, the old condom and its contents should be assumed to be still infectious. Therefore the old condom must be properly disposed of. A new condom should be used for each act of intercourse, as multiple usage increases the chance of breakage, defeating the primary purpose as a barrier.

Types and their pathogenic causes

Most of the diseases on this list are most commonly transmitted sexually. Some are commonly transmitted in other ways as well; for example, HIV/AIDS is also commonly transmitted through the sharing of infected needles by drug users, while SARS, which can be spread through casual contact such as coughing and sneezing, is very often not associated with sexual activity.

Bacterial

* Bacterial Vaginosis (BV) - not officially an STD but affected by sexual activity.
* Chancroid (Haemophilus ducreyi)
* Donovanosis (Granuloma inguinale or Calymmatobacterium granulomatis)
* Gonorrhea (Neisseria gonorrhoeae)
* Lymphogranuloma venereum (LGV) (Chlamydia trachomatis serotypes L1, L2, L3. See Chlamydia)
* Non-gonococcal urethritis (NGU) (Ureaplasma urealyticum or Mycoplasma hominis)
* Staphylococcal infection (Staphylococcus aureus, MRSA) - Sexually transmissible.
* Syphilis (Treponema pallidum)

Fungal

* Tinea cruris "Jock Itch" (Trichophyton rubrum and others). - Sexually transmissible.
* Yeast Infection

Viral

* Adenoviruses thought to contribute to obesity - venereal fluids (also fecal & respiratory fluids)
* Viral hepatitis (Hepatitis B virus) - saliva, venereal fluids.
(Note: Hepatitis A and Hepatitis E are transmitted via the fecal-oral route; Hepatitis C (liver cancer) 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
o Herpes simplex virus 1 may be linked to Alzheimer's disease.
* HIV/ AIDS (Human Immunodeficiency Virus) - venereal fluids
* HTLV 1, 2 - venereal fluids
* Genital warts - ("low risk" types of Human papillomavirus HPV) - skin and muscosal, transmissible with or without visible warts
* Cervical cancer, anal cancer - ("high risk" types of Human papillomavirus HPV) - skin and muscosal
* Molluscum contagiosum (molluscum contagiosum virus MCV) - close contact
* mononucleosis
o (Cytomegalovirus CMV - Herpes 5) - saliva, sweat, urine, feces and venereal fluids.
o (Epstein-Barr virus EBV - Herpes 4) - saliva
* Kaposi's sarcoma (Kaposi's sarcoma-associated herpesvirus KSHV - Herpes 8) - saliva

Parasites

* Pubic lice, colloquially known as "crabs" (Phthirius pubis)
* Scabies (Sarcoptes scabiei)

Protozoal

* Trichomoniasis (Trichomonas vaginalis)

Sexually transmitted enteric infections

Various bacterial (Shigella, Campylobacter, or Salmonella), viral (Hepatitis A, Adenoviruses), or parasitic (Giardia or amoeba) pathogens are transmitted by sexual practices that promote anal-oral contamination (fecal-oral). Sharing sex toys without washing or multiple partnered barebacking can promote anal-anal contamination. Although the bacterial pathogens may coexist with or cause proctitis, they usually produce symptoms (diarrhea, fever, bloating, nausea, and abdominal pain) suggesting disease more proximal in the GI tract.

Sexually transmissible oral infections

Common colds, influenza, Staphylococcus aureus, E. coli, Adenoviruses, Human Papillomavirus, Oral Herpes (1, 2 & 4, 5, 8), Hepatitis B and the yeast Candida albicans can all be transmitted through the oral route.