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Sexually transmitted infections (STI), also referred to as sexually transmitted diseases (STD) and venereal diseases (VD), are infections that are commonly spread by sex, especially vaginal intercourse, anal sex and oral sex. Most STIs initially do not cause symptoms.〔 This results in a greater risk of passing the disease on to others. Symptoms and signs of disease may include vaginal discharge, penile discharge, ulcers on or around the genitals, and pelvic pain. STIs acquired before or during birth may result in poor outcomes for the baby. Some STIs may cause problems with the ability to get pregnant.〔 More than 30 different bacteria, viruses, and parasites can cause STIs.〔 Bacterial STIs include chlamydia, gonorrhea, and syphilis among others. Viral STIs include genital herpes, HIV/AIDS, and genital warts among others. Parasitic STIs include trichomoniasis among others. While usually spread by sex, some STIs can also be spread by non-sexual contact with contaminated blood and tissues, breastfeeding, or during childbirth.〔 STI diagnostic tests are easily available in the developed world, but this is often not the case in the developing world.〔 The most effective way of preventing STIs is by not having sex.〔 Some vaccinations may also decrease the risk of certain infections including hepatitis B and some types of HPV.〔 Safer sex practices such as use of condoms, having a smaller number of sexual partners, and being in a relationship where each person only has sex with the other also decreases the risk.〔 Circumcision in males may be effective to prevent some infections.〔 Most STIs are treatable or curable.〔 Of the most common infections, syphilis, gonorrhea, chlamydia, trichomoniasis are curable, while herpes, hepatitis B, HIV/AIDS, and HPV are treatable but not curable.〔 Resistance to certain antibiotics is developing among some organisms such as gonorrhea. In 2008, it was estimated that 500 million people were infected with either syphilis, gonorrhea, chlamydia or trichomoniasis. At least an additional 530 million people have genital herpes and 290 million women have human papillomavirus.〔 STIs other than HIV resulted in 142,000 deaths in 2013. In the United States there were 19 million new cases of sexually transmitted infections in 2010.〔(【引用サイトリンク】url=http://www.cdc.gov/std/stats10/trends.htm )〕 Historical documentation of STIs date back to at least the Ebers papyrus around 1550 BC and the Old Testament. There is often shame and stigma associated with these infections.〔 The term ''sexually transmitted infection'' is generally preferred over the terms ''sexually transmitted disease'' and ''venereal disease'', as it includes those who do not have symptomatic disease. == Classification == Until the 1990s, STIs were commonly known as ''venereal diseases'', the word ''venereal'' being derived from the Latin word venereus, and meaning relating to sexual intercourse or desire, ultimately derived from Venus, the Roman goddess of love.〔(【引用サイトリンク】publisher=dictionary.reference.com )〕 "Social disease" was a phrase used as a euphemism. The World Health Organization (WHO) has recommended ''sexually transmitted infection'' as the preferred term since 1999.〔 ''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 a significant portion of 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.'' Most of the time, people do not know that they are infected with an STI until they are tested or start showing symptoms of disease. 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 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, HPV it was transmitted to him/her by means of sexual contact. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sexually transmitted infection」の詳細全文を読む スポンサード リンク
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