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== Classification and terminology ==
== Classification and terminology ==
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== Pathology ==
== Pathology ==

Revision as of 14:49, 8 December 2008

Sexually transmitted infection
SpecialtyInfectious diseases Edit this on Wikidata

A sexually transmitted disease (STD) 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. Increasingly, the term sexually transmitted infection (STI) is used, 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

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Pathology

Many STIs are (more easily) transmitted through the mucous membranes of the penis, vulva, rectum, urinary tract and (less often)[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.[1]

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 this chart [1], 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. 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.

Recent epidemiological studies have investigated the networks that are defined by sexual relationships between individuals, and discovered that the properties of sexual networks are crucial to the spread of sexually transmitted diseases. In particular, assortative mixing between people with large numbers of sexual partners seems to be an important factor.

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.

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Prevention

Main article: Safe sex

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 equals no risk. Not all sexual activities involve contact: cybersex, phonesex or masturbation from a distance are methods of avoiding contact. Ideally, both partners should get tested for STIs before initiating sexual contact, or if a partner engaged in contact with someone else, but even then, certain STIs, particularly certain persistent viruses like HPV, may be impossible to detect with current medical procedures as they may be asymptomatic. Prevention is also key in addressing viral STIs such as HIV & herpes, as they are currently incurable. Many diseases that establish permanent infections can so occupy the immune system that other diseases become more easily transmitted.

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 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. An infected fluid to broken skin borne direct transmission of HIV would not be considered "sexually transmitted", but can still theoretically occur during sexual contact, this can be avoided simply by not engaging in sexual contact when having open bleeding wounds. 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.[dubious – discuss] However, there have been cases of condom recall, as in a case in South Africa.[2]

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 STI's, 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. Defeated barrier equals potential transmission.

Testing

Main article: STD testing

Treatment history

American poster propaganda targeted at World War II soldiers and sailors appealed to their patriotism in urging them to protect themselves. The text at the bottom of the poster reads, "You can't beat the Axis if you get VD." Images of women were used to catch the eye on many VD posters.
File:Stdspain.jpg
Spanish Civil War poster, produced by the Republican government, saying "Avoid venereal diseases ... As dangerous as enemy bullets"

Prior to the invention of modern medicines, sexually transmitted diseases were generally incurable, and treatment was limited to treating the symptoms of the disease. The first voluntary hospital for venereal diseases was founded in 1746 at London Lock Hospital.[3]

The first effective treatment for a sexually transmitted disease was salvarsan, a treatment for syphilis. With the discovery of antibiotics, a large number of sexually transmitted diseases became easily curable, and this, combined with effective public health campaigns against STDs, led to a public perception during the 1960s and 1970s that they have ceased to be a serious medical threat.

During this period, the importance of contact tracing in treating STIs was recognized. By tracing the sexual partners of infected individuals, testing them for infection, treating the infected and tracing their contacts in turn, STI clinics could be very effective at suppressing infections in the general population.

In the 1980s, first genital herpes and then AIDS emerged into the public consciousness as sexually transmitted diseases that could not be cured by modern medicine. AIDS in particular has a long asymptomatic period — during which time HIV (the human immunodeficiency virus, which causes AIDS) can replicate and the disease can be transmitted to others — followed by a symptomatic period, which leads rapidly to death unless treated. Recognition that AIDS threatened a global pandemic led to public information campaigns and the development of treatments that allow AIDS to be managed by suppressing the replication of HIV for as long as possible. Contact tracing continues to be an important measure, even when diseases are incurable, as it helps to contain infection.

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

Fungal

Viral

Parasites

Protozoal

Sexually transmitted enteric infections

Various bacterial (Shigella, Campylobacter, or Salmonella), viral (Hepatitis A), 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.

See also

References

  1. ^ Virus Pathogenesis
  2. ^ Condom recall hits South African AIDS campaign - CNN.com
  3. ^ Archives in London and the M25 area (AIM25) London Lock Hospital records
  4. ^ Cook H, Furuya E, Larson E, Vasquez G, Lowy F (2007). "Heterosexual transmission of community-associated methicillin-resistant Staphylococcus aureus". Clin Infect Dis. 44 (3): 410–3. doi:10.1086/510681. PMID 17205449.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ Adenoviruses - Stanford University
  6. ^ Workowski K, Berman S (2006). "Sexually transmitted diseases treatment guidelines, 2006". MMWR Recomm Rep. 55 (RR-11): 1–94. PMID 16888612. {{cite journal}}: External link in |title= (help)
  7. ^ Wu J, Chen C, Sheen I, Lee S, Tzeng H, Choo K (1995). "Evidence of transmission of hepatitis D virus to spouses from sequence analysis of the viral genome". Hepatology. 22 (6): 1656–60. PMID 7489970.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ Farci P. "Delta hepatitis: an update". J Hepatol. 39 Suppl 1: S212–9. PMID 14708706.
  9. ^ Shukla N, Poles M (2004). "Hepatitis B virus infection: co-infection with hepatitis C virus, hepatitis D virus, and human immunodeficiency virus". Clin Liver Dis. 8 (2): 445–60, viii. doi:10.1016/j.cld.2004.02.005. PMID 15481349.
  10. ^ Alzheimer's linked to cold sores: study - ABC News (Australian Broadcasting Corporation)
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