引言位置：
https://en.wikipedia.org/wiki/Wikipedia:WikiProject_Medicine/Translation_task_force/RTT/Simple_STI
英文長條目：
https://en.wikipedia.org/wiki/Sexually_transmitted_infection
中文翻譯：
https://zh.wikipedia.org/wiki/%E6%80%A7%E6%84%9F%E6%9F%93%E7%96%BE%E7%97%85
<!--英文引言內容與翻譯-->
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.[1] This results in a greater risk of passing the disease on to others.[2] 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.[1]
’’’性感染疾病’’’（{{lang|en|Sexually transmitted infections}}，’’’STI’’’），又稱’’’性病’’’或’’’花柳病’’’，描述因性行為（尤指陰道性行為、肛交和口交）而傳播的疾病。大多數的性感染疾病一開始沒有症狀[1]，造成不知情的帶原者有極大的風險會傳染給他人[2]。性病的症狀包含：陰道分泌物、陰莖分泌物、性器官或其週邊潰瘍、以及骨盆疼痛。出生時或出生前感染性感染病將對胎兒造成不良影響。有的性感染病甚至導致影響生育能力的問題。
More than 30 different bacteria, viruses, and parasites can cause STIs.[1] Bacterial STIs include chlamydia, gonorrhea, and syphilisamong others. Viral STIs include genital herpes, HIV/AIDS, and genital warts among others. Parasitic STIs include trichomoniasisamong 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.[1] STI diagnostic tests are easily available in the developed world, but this is often not the case in the developing world.[1]
超過30種以上不同的細菌、病毒和寄生物能造成性感染病。細菌性的性感染病，包括衣原菌感染、淋病和梅毒。病毒性性感染病包括性器皰疹、後天性免疫不全／愛滋病、以及性器疣?。寄生病原性性感染病，包括陰道滴蟲炎等。儘管一般是經由性行為而散布感染、但是非性接觸、例如污染的血液和組織、哺育母乳或是分娩等、也可能引起一部分性感染病。在已開發國家中易進行性感染病的診斷，但在開發中國家則不易檢驗[1]．
The most effective way of preventing STIs is by not having sex.[3] Some vaccinations may also decrease the risk of certain infections including hepatitis B and some types of HPV.[3] 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.[1][3] Circumcision in males may be effective to prevent some infections.[1] Most STIs are treatable or curable.[1] Of the most common infections, syphilis, gonorrhea, chlamydia, trichomoniasis are curable, while herpes, hepatitis B, HIV/AIDS, and HPV are treatable but not curable.[1]Resistance to certain antibiotics is developing among some organisms such as gonorrhoea.[4]
預防性感染病最有效方式為避免性生活。某些疫苗或許可以降低一定感染風險，包括B型肝炎和某些型態的HPV。使用保險套，擁有較少的性伴侶或固定性伴侶等較安全的性行為同樣可以減輕感染危險。男性切除包皮對於預防某些感染可能是有效的。大部分的性感染病是可以治療或治癒。大部分的一般感染，例如淋病、梅毒、衣原體、陰道滴蟲炎是可以治癒，而皰疹、B型肝炎、後天性免疫不全/愛滋病雖然無法治癒，則是可以加以治療。某些治療特定感染病的抗生素，如淋病抗體，正在研發中。[4]
In 2008, it was estimated that 500 million people were infected with either syphilis, gonorrhea, chlamydia or trichomoniasis.[1] At least an additional 530 million people have genital herpes and 290 million women have human papillomavirus.[1] STIs other than HIV resulted in 142,000 deaths in 2013.[5] In the United States there were 19 million new cases of sexually transmitted infections in 2010.[6] Historical documentation of STIs date back to at least the Ebers papyrus around 1550 BC and the Old Testament.[7] There is often shame and stigma associated with these infections.[1] 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.[8]
2008年估計有5億人感染了梅毒、淋病、衣原体或滴虫病[1]，至少還有5.3億人有生殖器疱疹，另外2.9億的女性罹患有[[人類乳突病毒]]。後天性免疫不全以外的性病在2013年造成了14萬2千人死亡[5]。2010年美國的性傳染疾病患者增加了一千九百萬人[6]。有關性傳染疾病的歷史可以追溯到西元前1550年的{{le|埃伯斯氏古医籍|Ebers papyrus}}及[[舊約聖經]]，那時候罹患性傳染疾病是一種羞辱[1]。無論性感染是否造成症狀表現出疾病徵象，仍可被稱為「性感染疾病」[8]。
<!--長條目接續-->
<Classification>
<分類>
A poster from the Office for Emergency Management. Office of War Information, 1941-1945
Until the 1990s,[citation needed]
(附上圖片?)
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.[10] "Social disease" was a phrase used as a euphemism.
性病一般被認為是經性交傳染的疾病，veneral 來自拉丁語 venereus，與性交或慾望相關，衍生自羅馬愛神維納斯的典故[10]。也有委婉的說法稱之為"社交疾病"。
The World Health Organization (WHO) has recommended sexually transmitted infection as the preferred term since 1999.[9] Sexually transmitted infection is a broader term than sexually transmitted disease.[11] 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.[12]
世界衛生組織已於1999年起建議性感染病(sexually transmitted infection)為正式名稱[9]。STIs會比STD更為廣義[11]。所謂的感染(Infection)，指的是寄生物所形成的群落，很多時候這樣的群落並沒有任何副作用。而疾病(Disease)，指的是感染造成了損傷或不正常的機能。但很多時候並沒有任何症狀或徵候。深入認識像是HPV的感染之後，就能理解STI的使用會更為正確，像是HPV感染了很大一部份性生活活躍的人，但其實只有很少的人會因此而導致疾病。公共衛生單位其實一開始所推廣的名稱為STI，不過漸漸地臨床醫療人員為了與前項區別，開始使用STD[12]。
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.
性傳染疾病指的是那些已經造成疾病的感染，或是STI關聯性較弱的同義字。大多時候，直到透過檢驗或出現相關症狀，人們並不知道自己已經被性傳染病感染。更有甚者，STD常常出現在對於"傳染"定義不夠嚴謹的地方。例如，腦膜炎可以經由性接觸傳染，但因為性接觸並非此病原體最主要的傳染途徑，所以並不被視為性傳染疾病。這樣的差異是因為有其他傳染途徑比性接觸更為被重視。一般而言，性傳染疾病只有很微乎其微的機率，會經由除了性接觸以外的其他途徑傳染，現實上也比較可能因為性接觸而傳染(比較複雜的傳染途徑，包括輸血、共用皮下針，並不在考量中)。因此，我們可以這麼說，當一個人得到性傳染病，例如衣原體、淋病、皰疹，人類乳突狀病毒，大多經由性接觸而傳染給他/她的。
<Signs and symptoms>
<症狀與徵候>
Not all STIs are symptomatic, and symptoms may not appear immediately after infection. In some instances a disease can be carried with no symptoms, which leaves a greater risk of passing the disease on to others. Depending on the disease, some untreated STIs can lead to infertility, chronic pain or even death.[13]
並不是所有的性傳染病都有症狀，而且症狀也很少在感染後立刻出現。有些疾病帶原時並不會有症狀，這也增加了傳染給他人的可能。隨著疾病不同，有些未治療的性傳染病可能導致不孕、慢性疼痛甚至死亡[13]。
<Cause>
A.Transmission
The risks and transmission probabilities of sexually transmitted diseases are summarized by act in the table:[14][15][16][17][18][19][20][21][22][23][24][25][26]
A.傳染途徑
不同性行為方式在性傳染疾病上的風險及感染機率條列如下[14][15][16][17][18][19][20][21][22][23][24][25][26]
{| class="wikitable" style = "float: text-align:center"
! colspan="4" style="background:lightgrey; font-size:120%;"| 和受感染者進行未保護性行為風險
|-
|
! scope="col" | 已知風險
! scope="col" | 可能的風險
|-
! scope="row" | [[陰莖口交]]（對女性的影響）
|
*咽喉{{le|衣原體感染|Chlamydia infection}}[14]
*咽喉[[淋病]][14]（25–30%）
*[[單純疱疹|疱疹]]（少見）
*[[人類乳突病毒|HPV]][15]
*[[梅毒]][14]（1%）[16]
|
*[[B型肝炎]]（低風險）[17]
*[[人類免疫缺陷病毒|HIV]]（0.01%）[18]
*[[C型肝炎]]（不明）
|-
! scope="row" | [[陰道口交]]（對男性的影響）
|
*[[單純疱疹|疱疹]]
*[[人類乳突病毒|HPV]][15]
|
*咽喉[[淋病]][14]
*咽喉{{le|衣原體感染|Chlamydia infection}}[14]
|-
! scope="row" | [[陰莖口交]]（對男性的影響）
|
*{{le|衣原體感染|Chlamydia infection|衣原體}}
*[[淋病]][14]
*[[單純疱疹|疱疹]]
*[[梅毒]][14]（1%）[16]
|
*[[人類乳突病毒|HPV]]
|-
! scope="row" | [[陰道口交]]（對女性的影響）
|
*[[單純疱疹|疱疹]]
|
*[[人類乳突病毒|HPV]]
*[[細菌性陰道病]][14]
*[[淋病]][14]
|-
! scope="row" | [[人類性行為|陰道性交]]（對男性的影響）
|
*{{le|衣原體感染|Chlamydia infection|衣原體}}（30–50%）[17]
*[[陰蝨]]
*[[疥瘡]]
*[[淋病]]（22%） [19]
*[[B型肝炎]]
*[[單純疱疹|疱疹]]（第2型疱疹為0.07%）[20]
*[[人類免疫缺陷病毒|HIV]]（0.05%）[18][20]
*[[人類乳突病毒|HPV]]（高[17]，約40-50%）[21]
*{{le|人型支原体感染|Mycoplasma hominis infection}}[27][28][29][30]
*[[梅毒]]
*[[滴蟲性陰道炎]]
*{{le|解脲支原體感染|Ureaplasma infection}}[31][32]
|
*[[C型肝炎]]
|-
! scope="row" | [[人類性行為|陰道性交]]（對男性的影響）
|
*{{le|衣原體感染|Chlamydia infection|衣原體}}（30–50%）[17]
*[[陰蝨]]
*[[疥瘡]]
*[[淋病]]（22%） [19]
*[[B型肝炎]]
*[[單純疱疹|疱疹]]（第2型疱疹為0.07%）[20]
*[[人類免疫缺陷病毒|HIV]]（0.05%）[18][20]
*[[人類乳突病毒|HPV]]（高[17]，約40-50%）[21]
*{{le|人型支原体感染|Mycoplasma hominis infection}}[27][28][29][30]
*[[梅毒]]
*[[滴蟲性陰道炎]]
*{{le|解脲支原體感染|Ureaplasma infection}}[31][32]
|
*[[C型肝炎]]
|-
! scope="row" | [[人類性行為|陰道性交]]（對女性的影響）
|
*{{le|衣原體感染|Chlamydia infection|衣原體}}（30–50%）[17]
*[[陰蝨]]
*[[疥瘡]]
*[[淋病]]（47%） [22]
*[[B型肝炎]]（50–70%）
*[[單純疱疹|疱疹]]
*[[人類免疫缺陷病毒|HIV]]（0.1%）[18]
*[[人類乳突病毒|HPV]]（高[17]，約40-50%）[21]
*{{le|人型支原体感染|Mycoplasma hominis infection}}[27][28][30]
*[[梅毒]]
*[[滴蟲性陰道炎]]
*{{le|解脲支原體感染|Ureaplasma infection}}[31][32]
|
*[[C型肝炎]]
|-
! scope="row" | [[肛交]]（對男性的影響）
|
*{{le|衣原體感染|Chlamydia infection|衣原體}}
*[[陰蝨]]
*[[疥瘡]]（40%）
*[[淋病]]
*[[B型肝炎]]
*[[單純疱疹|疱疹]]
*[[人類免疫缺陷病毒|HIV]]（0.62%）[24]
*[[人類乳突病毒|HPV]]
*[[梅毒]]（14%）[16]
|
*[[C型肝炎]]
|-
! scope="row" | [[肛交]]（對女性的影響）
|
*{{le|衣原體感染|Chlamydia infection|衣原體}}
*[[陰蝨]]
*[[疥瘡]]
*[[淋病]]
*[[B型肝炎]]
*[[單純疱疹|疱疹]]
*[[人類免疫缺陷病毒|HIV]]（1.7%）[24]
*[[人類乳突病毒|HPV]]
*[[梅毒]]（1.4%）[16]
|
*[[C型肝炎]]
|-
! scope="row" | [[舐肛]]
|
*{{le|阿米巴性痢疾|Amebiasis}}
*[[隐孢子虫病]]（1%）
*{{le|梨形鞭毛蟲症|Giardiasis}}[33]
*[[A型肝炎]][34]]
*[[志賀桿菌病]][35]（1%）
|
*[[人類乳突病毒|HPV]] （1%）
|}
B.Bacterial
B. 細菌
*{{le| 軟性下疳|Chancroid}}（{{le|软性下疳嗜血杆菌|Haemophilus ducreyi}}）
*{{le|衣原體感染|Chlamydia infection}}（[[砂眼衣原體]]）
*[[淋病]]（[[淋球菌]]）
*{{le|性病肉芽肿|Granuloma inguinale}}（{{le|肉芽腫桿菌|Klebsiella granulomatis}}）
*{{le|生殖支原体|Mycoplasma genitalium}}[36][37][38]
*{{le|人型支原体|Mycoplasma hominis}}[27][28][29][30][39]
*[[梅毒]]（{{le|梅毒螺旋体|Treponema pallidum}}）
*{{le|解脲支原体感染|Ureaplasma infection}}[31][32]
C.Fungal
C真菌
*[[念珠菌症]]（酵母菌感染）
D.Viral
Micrograph showing the viralcytopathic effect of herpes (ground glass nuclear inclusions, multi-nucleation). Pap test. Pap stain.
D. 病毒
E.Parasites
E.寄生蟲
* [[陰蝨]]
* [[疥疮]]（{{le|人疥螨|Sarcoptes scabiei}}）
F.Protozoal
F.原生動物
* [[滴虫性阴道炎]]（{{le|陰道滴蟲|Trichomonas vaginalis}}）
G.Main types
Sexually transmitted infections include: 圖: Secondary syphilis
[[衣原體感染]]為由[[砂眼衣原體]]引起的性傳染疾病，女性可能有陰道分泌物異常、排尿灼熱感、異常陰道出血等症狀，甚至無症狀[44]；男性則可能有排尿疼痛、異常尿道分泌物等症狀[45]。若未接受任何治療，衣原體會引發泌尿道感染，進而可能造成[[骨盆腔發炎]]。骨盆腔發炎會造成懷孕期間嚴重併發症、導致不孕、或子宮外孕。然而，衣原體感染可藉由抗生素治癒。
造成[[皰疹]]最常見的病原體為單純性皰疹病毒（HSV）。第一型單純性皰疹病毒經由口腔傳染，多半會造成唇皰疹，第二型單純性皰疹病毒一般是透過性傳觸傳染，會影響性器官，不過也有第一型皰疹影響性器官，或是第二型皰疹影響唇部的情形[46]。有些人得到皰疹後，其症狀非常溫和，甚至沒有症狀。若有症狀的人，在暴露在皰疹病毒2至20天後會有明顯症狀，症狀會持續二週至四週。症狀包括小而有液體的水泡，頭痛，背痛，生殖器或肛門部位瘙癢或刺痛，排尿時疼痛，{{le|類似流感疾病|Influenza-like illness|類似流感症狀}}，淋巴結腫大，發燒等。皰疹是藉由和患者的皮膚接觸所造成，病毒從何處進入體內，就會在那個部份造成感染，包括接吻，陰道性行為，口交及肛交。當皰疹有可見症狀時，其感染力最強，不過沒有症狀的患者仍然會透過皮膚接觸而傳染疾病[47]。初次受到感染時，因身體沒有抗體，症狀最為嚴重，之後其他部份的感染可能症狀會比較輕微，甚至不會有後續的感染。皰疹無法治癒，但有抗病毒的療法，只處理其症狀，以及降低感染力（[[伐昔洛韦]]）。雖然HSV-1多半感染口腔，HSV-2多半感染性器官，但HSV-1也有可能從口腔傳染到性伴侶的性器官。這二種病毒會停留在脊柱頂部或底部的神經束上，產生口腔或是性器官的病毒感染。
*[[人類乳突病毒]]（HPV）是美國最常見的性傳染疾病[48]。人類乳突病毒超過40種，其中大部份都不會致病。90%的情形下，人體的免疫系統可以在二年內清除人類乳突病毒[49]。有些情形下，人體無法清除人類乳突病毒，會出現生殖器疣（生殖器周圍的疣可能是大小或小的，有突起或是平坦的，或是像花椰菜一樣的外形），子宮頸癌或是其他和人類乳突病毒有關的癌症。不過有時會到病情較後期才有相關症狀。婦女的子宮頸抹片檢查非常重要，可以檢查和治療癌症。有二種針對女性的[[人類乳突病毒疫苗]]，分別是{{le|保蓓|Cervarix}}及 {{le|嘉喜|Gardasil}}，可以預防人類乳突病毒的感染。人類乳突病毒可以透過性器官之間的性接觸感染，也會透過口交感染。需注意到受感染者可能不會有任何症狀。
*[[淋病]]是由[[淋病雙球菌]]傳播的，淋病雙球菌生活在尿道，陰道，直腸，口腔，喉嚨及眼睛等潮濕的黏膜組織中。淋病可以藉由和陰莖，陰道，口腔及肛門的接觸而感染。一般在接觸到患有淋病的性伴侶後，2至5天就會有淋病的症狀，不過也有些人沒有症狀長達一個月之久。男性的症狀包括排尿時的燒灼感及疼痛，頻尿，陰莖有白色，綠色或黃色的異常分泌物，尿道口紅腫，睪丸腫脹，以及喉嚨痛。女性的症狀有陰道異常分泌物，排尿時的燒灼感及瘙癢，性交時疼痛，若是感染擴散到輸卵管，會有腹部劇痛及發燒，不過也有許多女性沒有任何症狀[50]。有一些淋病的菌種已有抗藥性，不過大多數的情形仍可以用抗生素進行治療。
*[[梅毒]]是透過細菌感染的性感染疾病，若未接受治療會造成許多併發症，甚至會導致死亡[51]。臨床症狀包括泌尿生殖道，口腔及直腸潰瘍，若未乃時治療，症狀會進一步惡化。近年來，梅毒在西歐的罹患率正在下降，但在東歐（前蘇聯國家）正在上昇。在[[喀麥隆]]，[[柬埔寨]]及[[巴布亞新幾內亞]]等國，梅毒的患病率很高[52]。美國梅毒的患病率也正在增加[53]。
*[[滴蟲性陰道炎]]是一種常見的性傳染疾病，是由一種名為{{le|毛滴蟲|Trichomonas vaginalis}}的寄生性原生虫所傳染[54]，除了造成女性滴蟲性陰道炎外，也會造成男性尿道的感染，不過比例上仍以女性感染為主[55]。大部份的患者可以用抗生素{{le|甲硝唑|metronidazole}}治療，相當有效[56]。
*[[人類免疫缺陷病毒]]（HIV）會破壞[[免疫系統]]，攻擊{{le|CD4|CD4}}白血球細胞，使免疫系統無法抵抗致病原。人類免疫缺陷病毒會藉由體液傳播，因此會經由性行為而散播。HIV也可能透過受感染的血液製品、哺乳、生產，或是在懷孕是從母親傳染給胎兒[57]。受感染者在症狀最顯著的的時期，該症狀會稱為[[艾滋病]]（AIDS，免疫缺陷症候群）[58]。不過受人類免疫缺陷病毒感染時，也有不同的階段，分為原發感染、無症狀感染（隱性感染）、有症狀感染（顯性感染）及艾滋病。原發感染時，患者會有類似頭痛、疲倦、發燒及肌肉酸痛等類似流感的症狀，症狀約持續二週。在無症狀感染期，沒有相關症狀，病患有可能在幾年的時間都在無症狀期。當已進入有症狀感染時，人體的免疫系統已經減弱，而且CD4+ 的[[T细胞]]計數會下降。當人類免疫缺陷病毒已造成生命威脅時，此時即稱為艾滋病。艾滋病的患者因為免疫系統嚴重受損，很容易因為[[机会性感染]]而重病，甚至死亡[44]。當1980年代剛開始發現艾滋病時，患者很少有機會存活到數年以上。目前仍沒有可以治癒HIV或艾滋病的藥物，不過現在已有新的[[抗反轉錄病毒藥物]]來治療艾滋病感染，藉由降低病毒的數量，病患存活時間可以加長，不過即使病患體內的病毒數量很低，仍然可能將病毒傳播給其他人[59]。
H. Unscreened
There are many species of bacteria, protozoa, fungi, and viruses, many which remain undocumented or poorly studied with regards to sexual transmission. Despite that the above include what are generally known as STIs, sexually transmission of microbes is far from limited to the above list. Since the sexual route of transmission is not considered common, and/or the microbe itself is not implicated in a major research study on disease, the following pathogens are simply not screened for in sexual health clinics. Some of these microbes are known to be sexually transmittable.
H. 未受常規篩檢的疾病
有許多的細菌，原生动物，真菌及病毒還不確定是否會透過性行為散播，可能是出目前沒有文獻資料，或是相關研究還很少。除了上述提到的病原體以外，還有許多其他的疾病可能透過性行為傳染。在傳染病中，性行為的傳染途徑影響較小，而且這類的病原因目前不是疾病主要的研究領域，因此診所不會篩檢這些疾病，其中有些疾病已確定會透過性行為傳播。
Microbes known to be sexually transmissible (but not generally considered STDs/STIs) include:
以下是一些病原體，㑹藉由性行為而傳染疾病：
<Pathophysiology>
<病理生理學>
Many STIs are (more easily) transmitted through the mucous membranes of the penis, vulva, rectum, urinary tract and (less often—depending on type of infection) the mouth,throat, respiratory tract and eyes.[62] 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.[63] The amount of contact with infective sources which causes infection varies with each pathogen but in all cases a disease may result from even light contact from fluid carriers like venereal fluids onto a mucous membrane.
許多性傳染疾病很容易由[[陰莖]]、[[陰戶]]、[[直腸]]、[[泌尿道]]的[[黏膜]]進入體內，有些性傳染疾病也可能經由[[口腔]]、[[喉嚨]]、[[呼吸道]]及[[眼睛]]的[[黏膜]]入侵人體[62]。像[[龟头]]上的組織也是黏膜組織，只是不會分泌[[黏液]]而已（類似[[嘴唇]]的構造）。黏膜和皮膚不同，黏膜會讓一些致病源進入人體[63]。會造成感染的接觸次數視病原体而不同，不過即使是患病者的载液（精液或陰部分泌物）和黏膜的輕微接觸都有可能造成感染。
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.[64] 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.
上述原因可能是性傳染疾病由性行為傳播的比例遠高於其他接觸方式（如碰觸、擁抱、握手等）的原因之一，但這不是唯一的原因。像在口腔及性器官都有黏膜組織，但很多的性傳染疾病可能從口交傳播，但不會從深吻傳播。根據相關研究，很多性傳染疾病可能由口腔傳染到性器官，或是由性器官傳染到口腔，但很不容易從口腔傳染到口腔[64]。以HIV為例，性器官的分泌物中的致病原比[[唾液]]要高很多。有些性傳染疾病甚至會透過直接的皮膚接觸傳染，像[[单纯疱疹]]及[[人類乳突病毒]]都是這様的情形。
Depending on the STI, 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 than when they are absent. However, a person can spread HIV infection at any time, even if he/she has not developed symptoms of AIDS.
性傳染疾病的症狀和傳染力間的關係依疾病而不同。例如[[单纯疱疹]]在有[[水疱]]時傳染給他人的機率比沒有水疱時會高很多。不過HIV帶原者可能沒有任何艾滋病的症狀，但仍然會散播HIV。
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 STI 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 STI got it from contact (sexual or otherwise) with someone who had it, or his/her bodily fluids. Some STIs such as HIV can be transmitted from mother to child either during pregnancy or breastfeeding.
所有會和其他人的體液接觸的[[人類性行為|性行為]]，都有可能傳播性傳染疾病。目前大部份關注的焦點都集中在控制會帶艾滋病的HIV，但其他性傳染疾病會有不同的情形。性傳染疾病正如其名稱所述的，是由一個人和其他人之間的性行為所傳染的，不是因為進行性行為所導致的。[[細菌]]、[[真菌]]、[[原生動物]]或[[病毒]]是其致病原，若和沒有性傳染疾病的人進行性行為，是不會導致性傳染疾病的。相反的，若有人得到性傳染疾病，一定是接觸到和其他有性傳染疾病的患者
（可能是性接觸或是其他接觸）或是接觸到其體液。像HIV等性傳染疾病可能會藉由懷孕或是哺乳，由母親傳染給嬰兒。
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 STIs, i.e., "giving" or "receiving" are both risky although receiving carries a higher risk.
雖然不同的性行為傳染各種性傳染疾病的可能性有很大的變異，不過二人（或二人以上）的的性行為都是雙向傳染性傳染疾病的途徑。
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.
醫療專家一般會建議進行[[安全性行為]]（如使用[[保險套]]），在性行為中減少得到性傳染疾病的風險。不過安全性行為不能視為絕對的安全。其他會輸送體液或是暴露於其他人體液的行為，例如[[輸血]]或接受血液製品、共用針頭、被針頭刺傷（例如醫護人員在醫療過程中意外被刺傷）、共用[[刺青]]用的針，分娩等都是可能的傳染途徑。因此一些族群的風險會隨之提高，例如醫護人員、[[血友病]]患者，或是吸毒者等。
Recent epidemiological studies have investigated the networks that are defined by sexual relationships between individuals, and discovered that the properties of sexual networksare 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.
近來的[[流行病學]]研究在調查由個體之間的性關係所形成的網絡，發現[[性网络]]對性傳染疾病的傳播十分關鍵。特別是有很多性伴侶者之間的{{le|近似節點配對|assortative mixing}}是一個重要因素。
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.
性傳染疾病的患者可能沒有任何症狀，但仍然會散播疾病。而染有傳染疾病的女性常會有嚴重的{{le|盆腔炎pelvic inflammatory disease}}症狀。
<Prevention>
圖San Francisco City Clinic a municipal STI testing center in San Francisco.
Prevention is key in addressing incurable STIs, such as HIV and herpes. Sexual health clinics promote the use of condoms and provide outreach for at-risk communities.
The most effective way to prevent sexual transmission of STIs is to avoid contact of body parts or fluids which can lead to transfer with an infected partner. Not all sexual activities involve contact: cybersex, phonesex or masturbation from a distance are methods of avoiding contact. Proper use of condoms reduces contact and risk. Although a condom is effective in limiting exposure, some disease transmission may occur even with a condom.[65]
若要處理像愛滋病之類無法治癒的性傳播疾病，預防非常重要。[[性健康診所]]提倡使用保險套，及針對高風險社群提供外展服務。
若要避免感染或傳播性傳播疾病，最有效的方式是避免接觸受感染者的[[性器官]]或是像血液或精液等體液，不是所有的性活動都有肢體接觸，像[[網路調情]]、[[電話調情]]及保持一定距離的[[自慰]]都沒有肢體接觸，以正確方式使用[[保險套]]也可以減少接觸及感染的風險，不過即使性交時有戴保險套，仍可能有感染某些特定的性傳播疾病[65]。
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.
性伴侶在第一次性行為前，需檢查是否有性傳播疾病，若中間有和其他人進行過性行為，需再進行檢查。有些感染在初期是檢查不到的（即空窗期），因此需要等一段足夠的時間再進行檢查。有些性傳染疾病，特別是像人類乳突病毒之類持久性病毒，無法用現有的醫療技術檢查出來。
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.
許多永久性傳染的疾病也會影響免疫系統，因此患者也會容易感染其他疾病。若HIV病毒的計數很少時，[[先天免疫系統]]中針對HIV病毒的[[防禦素]]可以避免HIV病毒的傳播，不過若先天免疫系統已受到其他疾病的影響，就容易罹患愛滋病。一些病毒的性傳播疾病也會大幅增加愛滋病病患的死亡率。
A.Vaccines
Vaccines are available that protect against some viral STIs, such as Hepatitis A, Hepatitis B, and some types of HPV. Vaccination before initiation of sexual contact is advised to assure maximal protection.
A.疫苗
有些病毒性的性傳染播病有對應疫苗，例如{{le|A型肝炎疫苗|Hepatitis A vaccine}}、[[B型肝炎疫苗]]及針對某些乳突病毒的[[人類乳突病毒疫苗]]，若要達到最大的保護效果，需要在初次性接觸前就施打疫苗。
B.Condoms
Condoms and female 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 STIs.
B.保險套
[[保險套]]（含[[女用保險套]]）若正常使用時有保護效果。但只能保護保險套覆蓋到的部份，沒被保險套遮蓋住的部份仍有可能受到感染而患病。
In the case of HIV, sexual transmission routes almost always involve the penis, as HIV cannot spread through unbroken skin; therefore, properly shielding the penis with a properly worn condom from the vagina or 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 presenting open, bleeding wounds.
以 HIV病毒為例，因為HIV病毒無法穿過無傷口的皮膚，傳染的路徑幾乎都包括陰莖。若以正確方式在陰莖上穿戴保險套，不論進行陰道性交或肛交時，都可以有效避免HIV病毒的傳播。不過若皮膚有傷口，接觸到患者的體液，有可能讓HIV病毒傳播，此情形一般不算是「性傳播」，但在性接觸時理論上可能會發生。只要在生殖器官有流血傷口時不進行性接觸，即可避免此一情形。
Other STIs, even viral infections, can be prevented with the use of latex, polyurethane or polyisoprene 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 or synthetic condoms.
其他的性傳播疾病（甚至包括病毒感染）可以藉由使用[[乳膠]]、[[聚氨酯]]或[[聚異戊二烯]]的保險套來作為阻隔。有些微生物或病毒很小，可以穿過自然材質的保險套，但仍無法穿過乳膠或是合成橡胶類的保險套。
Proper male condom usage entails:
男性保險套正確的使用方式有以下數點：
In order to best protect oneself and the partner from STIs, the old condom and its contents should be assumed to be 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 effectiveness as a barrier.
為了避免自身及性怑侶得到性傳染疾病，用過的保險套及其內容物需視為有感染性的，因此需謹慎丟棄。新的保險套在每次性行為中只能使用一次，重覆使用有可能會破裂，無法發揮阻隔作用。
C. Nonoxynol-9
Researchers had hoped that nonoxynol-9, a vaginal microbicide would help decrease STI risk. Trials, however, have found it ineffective[66] and it may put women at a higher risk of HIV infection.[67]
C.壬苯醇醚-9
{{link-en|壬苯醇醚-9|nonoxynol-9}}是一種陰道用的{{link-en|殺微生物藥|Microbicide}}，研究者原希望壬苯醇醚-9可以減少感染性傳播疾病的風險，不過後來發現沒有效果[66]，而且還提高女性感染HIV的風險[67]。
<Screening>
Sexually active women under the age of 25 and those over 25 with risk should be screened for chlamydia and gonorrhea yearly.[68] After being treated for gonorrhea all people should be re tested for the disease after three months.[68]
<篩檢>
25歲以下，性行為活躍的女性，或是25歲以上，罹患衣原体和淋病風險較高的女性，需每年接受相關的篩檢[68]。在淋病治癒後，也需每三個月接受一次檢查[68]。
Nucleic acid amplification tests are the recommended method of diagnosis for gonorrhea and chlamydia.[69] This can be done on either urine in both men and women, vaginal or cervical swabs in women, or urethral swabs in men.[69]
{{le|核酸擴增檢測|Nucleic acid amplification tests}}是衣原体和淋病的建議檢測方式[69]。可以用男性或女性的尿液、女性的阴道或宫颈抹片、或是男性的尿道抹片來檢查[69]。
<Diagnosis>
World War II US Army poster warning of venereal disease
Testing may be for a single infection, or consist of a number of tests for a range of STIs, including tests for syphilis, trichomonas, gonorrhea,chlamydia, herpes, hepatitis and HIV. No procedure tests for all infectious agents.
可以針對單一的性傳染疾病進行{{le|醫學檢查|Medical test}}，也有針對一些性傳染疾病進行的多項檢查，範圍包括[[梅毒]]、[[滴虫]]、[[淋病]]、[[衣原体]]、[[疱疹]]、[[肝炎]]和[[HIV]]，不過還沒有針對所有性病的檢查。
STI tests may be used for a number of reasons:
性傳染疾病檢查的原因包括以下幾項：
*為了確認症狀及疾病原因的{{le|診斷檢查|diagnostic test}}。
*為了預防無症狀感染或是症狀前感染的或及疾病原因的{{le|篩檢|Screening (medicine)}}。
*為了檢測未來的性伴侶沒有相關疾病，這多半是在計劃要進行非[[安全性行為]]（如[[無套性交]]）、要開始長期單一性伴侶的性關係，或是要生育時進行。
*在懷孕前或是懷孕中檢測，以免性傳染疾病傷害嬰兒。
*在嬰兒出生後檢測，確認嬰兒是否有從母體傳染到性病。
*避免使用到性傳染疾病捐贈的[[捐血|血液]]及[[器官捐贈|器官]]。
*已知感染者{{le|接觸者追蹤|Contact Tracing}}流程的一部份。
*大規模[[流行病學]]追蹤的一部份。
Early identification and treatment results in less chance to spread disease, and for some conditions may improve the outcomes of treatment. There is often a window period after initial infection during which an STI test will be negative. During this period, the infection may be transmissible. The duration of this period varies depending on the infection and the test. Diagnosis may also be delayed by reluctance of the infected person to seek a medical professional. One report indicated that people turn to the Internet rather than to a medical professional for information on STIs to a higher degree than for other sexual problems.[70]
性傳染疾病早期的識別及治療可以讓疾病比較不容易擴散，有時也有助於疾病的治癒。有些性傳染疾病存在{{le|空窗期|Window period}}，在初次感染後，在一段時間內檢測結果會是陰性（未罹患疾病），但其實已有罹患疾病，而且已有感染力。空窗期的時期隨疾病種類及檢測方式而不同。診斷也可能因為受感染者不願意就醫而往後延。有一個報告指出，在罹患性傳染疾病時，人們更容易上網找尋相關資料，而不願意就醫，其比例較其他性問題的比例要高[70]。
Management
處置
High-risk exposure such as that which occurs in rape cases may be treated preventatively using antibiotic combinations such as azithromycin, cefixime, and metronidazole.
An option for treating partners of patients (index cases) diagnosed with chlamydia or gonorrhea is patient-delivered partner therapy, which is the clinical practice of treating the sex partners of index cases by providing prescriptions or medications to the patient to take to his/her partner without the health care provider first examining the partner.[71]
高感染風險的情形（例如被強暴）會預防性地使用多種抗生素，如[[阿奇霉素]]、[[头孢克肟]]及{{le|甲硝脞|metronidazole}}。
若是病患（[[指示病例]]）患{{le|衣原體感染|Chlamydia infection}}或是[[淋病]]，有一種針對其性伴侶的治療方式是{{le|"病人交付的伴侶療法|patient-delivered partner therapy|伴侶療法}}，也就是將藥物給予患者，再將藥物交付給伴侶的做法[71]。
<Epidemiology>
<流行病學>
圖Age-standardized, disability-adjusted life years for STDs (excluding HIV) per 100,000 inhabitants in 2004.[72]
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.[73]
性傳染病的診斷及治療都有許多進步，許多病患都可以得到治療，使得疾病不具感染力，甚至可以治癒，不過性傳染疾病的罹患比率仍居高不下。由於性道德的改變以及口服避孕藥的出現，使得在許多文化中，性行為已不會受到如同以往一樣的限制（尤其對女性更是如此），而醫生和病人之間也很難公開及坦誠的處理性方面的議題。而且[[抗藥性細菌]]（如抗盤尼西林的[[淋球菌]]）的出現及擴散更使得性傳染病難以治療。像旅行就是1970年代[[愛滋病]]病毒（[[HIV-1]]）從非洲及歐洲快速擴散到美洲的主要原因之一[73]。
Commonly reported prevalences of STIs among sexually active adolescent girls both with and without lower genital tract symptoms include chlamydia (10–25%), gonorrhea (3–18%), syphilis (0–3%), Trichomonas vaginalis (8–16%), and herpes simplex virus (2–12%).[citation needed] Among adolescent boys with no symptoms of urethritis, isolation rates include chlamydia (9–11%) and gonorrhea (2–3%).[citation needed] A 2008 CDC study found that 25–40% of U.S. teenage girls has a sexually transmitted disease.[74][75]
在性行為活躍的少女中（不考慮是否有生殖道症狀），常見的性傳播疾病有[[衣原體感染]]（10-25%）、[[淋病]]（3–18%）、[[梅毒]]（0–3%）、[[滴蟲]]（8–16%）及[[單純皰疹病毒]]（2–12%）。在性行為活躍，且沒有尿道炎症狀的的少年中，常見的性傳播疾病有衣原體（9–11%）及淋病（2–3%）。2008年[[美國疾病控制與預防中心]]]的研究指出，美國少女有25–40%有性傳播疾病[74][75]。
AIDS is among the leading causes of death in present-day Sub-Saharan Africa.[76] HIV/AIDS is transmitted primarily via unprotected sexual intercourse. More than 1.1 million persons are living with HIV/AIDS in the United States,[77] and it disproportionately impacts African Americans.[78] Hepatitis B is also considered a sexually transmitted disease because it can be spread through sexual contact.[79] The highest rates are found in Asia and Africa and lower rates are in the Americas and Europe.[80] Approximately two billion people worldwide have been infected with the hepatitis B virus.[81]
[[艾滋病]]是現今[[撒哈拉以南非洲]]主要的死因之一[76]。後天性免疫不全／愛滋病可以藉由沒有防護的性行為而傳播。在美國約有110萬人[[美国艾滋病疫情|罹患艾滋病]][77]，在[[非裔美国人]]中罹患的比例明顯偏高[78]。[[B型肝炎]]也會藉由性行為傳染，因此有時也會列為性病[79]，在亞洲及非洲的罹患比率最高，在美國及歐洲較少[80]。全世界約有20億人曾感染過B型肝炎[81]。
<History>
緣由
1930s Works Progress Administration poster
The first well-recorded European outbreak of what is now known as syphilis occurred in 1494 when it broke out among French troops besieging Naples in the Italian War of 1494–98.[82] The disease may have originated from the Columbian Exchange.[83] From Naples, the disease swept across Europe, killing more than five million people.[84] As Jared Diamond describes it, "[W]hen syphilis was first definitely recorded in Europe in 1495, its pustules often covered the body from the head to the knees, caused flesh to fall from people’s faces, and led to death within a few months," rendering it far more fatal than it is today. Diamond concludes,"[B]y 1546, the disease had evolved into the disease with the symptoms so well known to us today."[85]
1930年[[公共事业振兴署]]的海報
歐洲第一次有充份紀錄的性病（後來確認是[[梅毒]]）爆發是在1494年，在{{le|1494年至1498年的義大利戰爭Italian War of 1494–98|義大利戰爭}}中包圍[[那不勒斯]的法軍中所爆發[82]。此疾病可能從[[哥倫布大交換]]時引入[83]。疾病從那不勒斯起席捲了整個[[歐洲]]，死亡人數超過五百萬人[84]。[[槍炮、病菌與鋼鐵]]的作者[[賈德．戴蒙]]提到：「當1495年歐洲初次出現梅毒時，其皮膚病從頭部一直延伸到膝蓋，皮和肉㑹從病患的臉上剝落，幾個月後就會死亡。當時性病的致死率比現在高。
U.S. propaganda poster targeted atWorld War II servicemen appealed to their patriotism in urging them to protect themselves. The text at the bottom of the poster reads, "You can’t beat theAxis if you get VD."
美國針對二次大戰軍人時的宣傳海報，以其愛國心鼓勵其保護自已，在海報下面寫著：
”若你罹患性病，你無法戰勝[[軸心國]]"
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.[86] Treatment was not always voluntary: in the second half of the 19th century, the Contagious Diseases Acts were used to arrest suspected prostitutes. In 1924, a number of states concluded the Brussels Agreement, whereby states agreed to provide free or low-cost medical treatment at ports for merchant seamen with venereal diseases.
在現代醫學發明之前，大部份的性傳染疾病是無法治癒的，治療只是針對症狀的處理。第一個針對性病志願治療的診所是1746年成立的{{le|倫敦洛克診所|London Lock Hospital}}[86]。不過處理不全是志願性的，英國在1864年提出的{{le|感染疾病法案|Contagious Diseases Acts}}會逮捕可能受感染的娼妓。1924年許多國家訂定了{{le|布魯賽爾協定 (1924年)|Brussels Agreement (1924)|布魯賽爾協定}}，同意在港口針對商船船員免費提供低成本的性病藥物。
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 effectively suppress 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. HIV/AIDS entered the United States from Haiti in about 1969.[87] 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.
第一個可以有效治療性病的藥物是[[灑爾佛散]]，是治療梅毒的藥物。在[[抗生素]]發明後，大部份的性病皆可治癒，再加上當時對性病公共衛生政策的有效，1960及1970年代大眾普遍認為性病已不再是致命的健康威脅。
在那段期間，大眾也認可[[接觸追蹤]]在性病防治上的重要性。藉由追蹤受感染者的性伴侶，測試他們是否有感染，治療感染者，再追蹤其性伴侶……。藉由此方式可以抑制性病的大幅擴散。
1980年代，[[生殖器皰疹]]及[[艾滋病]]等現在醫學無法治癒的性病開始受到大眾的關切。尤其是艾滋病有一段較長的潛伏期，當時就有可能將艾滋病傳染紿其他人，之後才會出現相關症狀，若沒有治療，會很快死亡。艾滋病約在1987年從海地進入美國[87]。由於大眾對艾滋病認知為全球性的[[瘟疫]]，因此有較充足的公眾資訊。而治療上的進展也可以以盡量抑制HIV複制的方式控制艾滋病。雖然這些疾病無法治癒，但接觸追蹤可以減少感染人數，因此仍是重要的處理措施。
<!--目前中文頁面-->
性傳播疾病或性傳染疾病，又稱性病，指主要藉由性行為（包括口交及肛交等）為傳染途徑的傳染病。性病可能有很多起因：病毒、病菌、真菌和寄生蟲等。此外也有些疾病也會透過人類性行為傳染，但不一定列為性傳播疾病，例如B型肝炎。
近年也開始用性傳播感染來代替性傳染疾病，前者的範圍較廣[1]，一個人可能受到感染，甚至有可能感染給其他人，但本身沒有任何疾病的症狀。
有些性傳播疾病也會藉由注射藥品時的針頭共用，感染給其他人，或是經由生產、哺乳而傳播給下一代[2]。性傳播疾病廣為人知已有數百年的歷史．性病學則是醫學中有關性傳播疾病的相關研究。
<!--病理-->
性病的病原體一般比較脆弱，比如，反轉錄病毒很快就被環境中普遍存在的RNA酶降解，所以離開人體後很快就失去活性。性病的病原體只有人與人之間的親密行爲才能傳播。人類會在性接觸中受到感染是因為：陰莖與陰道有黏膜，黏膜容易破損出血，病源體（病毒或細菌）從黏膜進入人體要比從皮膚容易得多。因此人在性行為中受到感染要比其他管道（像是握手等等）更容易。
會直接接觸體液的性行為都有某種程度的風險。
許多不同的疾病會被歸到性病這一類，是因為其主要傳染途徑是性行為。但是這些疾病之中很多也可以由別的途徑傳染，例如肝炎、愛滋病等等也可以由輸血、針頭污染等性行為以外的途徑傳染[3][4]。
醫療健康專家建議採取安全性行為，例如正確使用保險套可以減低風險。還有人進一步認為禁慾和忠實單一性伴侶更能減低風險。禁慾（Abstinence）、忠實（Be Faithful）、戴套（Use a Condom），三者合稱ABC三原則，是許多國家的安全性行為教育政策[5]。
<!--治療-->
人類已認識性病數百年。藥發明之前，性病大多是無法治癒的，只能治療疾病的症狀。1747.1.31，英國倫敦Lock醫院開設第一所性病診所。
人類發明的第一個治療性病的方式是灑爾佛散，梅毒特效藥[6]。後來發明了抗生素，以類青黴素藥物注射盤尼西林或口服安比西林等進行10天以上每天四次的療程，許多性病都能輕易治療。加上有效的性病衛生宣導活動，1960年代到1970年代大家都以為性病威脅不再。
這段期間，性病治療開始重視接觸者追蹤。追蹤檢測一個感染者的性伴侶，然後治療其中的感染者，並且從此繼續追蹤下去，可以在群眾之中有效控制疫情。
1980年代，第一例皰疹二型與愛滋病這種現代醫藥無法治癒的疾病開始受到公共關切。特別是愛滋病有潛伏期[7]，可讓病毒繼續傳染給別人多年而不自知（沒有病徵），然後進入病發期，在無接受治療的情況下很快就會死亡。愛滋病可能造成全球大流行的認知帶動了大眾宣導活動以及研發治療方法，後來能夠抑制愛滋病病情一段時間。接觸者追蹤在這段時間仍然很重要。
<!--預防-->
若要處理像愛滋病之類無法治癒的性傳播疾病，預防非常重要。性健康診所提倡使用保險套，及針對高風險社群提供外展服務。
若要避免感染或傳播性傳播疾病，最有效的方式是避免接觸受感染者的性器官或是像血液或精液等體液，不是所有的性活動都有肢體接觸，像網路調情、電話調情及保持一定距離的自慰都沒有肢體接觸，以正確方式使用保險套也可以減少接觸及感染的風險，不過即使性交時有戴保險套，仍可能有感染某些特定的性傳播疾病[8]。
性伴侶在第一次性行為前需檢查是否有性傳播疾病，若中間有和其他人進行過性行為，需再進行檢查。有些感染在初期是檢查不到的（即空窗期），因此需要等一段足夠的時間再進行檢查。
許多永久性傳染的疾病也會影響免疫系統，因此患者也會容易感染其他疾病。若HIV病毒的計數很少時，先天免疫系統中針對HIV病毒的防禦素可以避免HIV病毒的傳播，不過若先天免疫系統已受到其他疾病的影響，就容易罹患愛滋病。一些病毒的性傳播疾病也會大幅增加愛滋病病患的死亡率。
<!--疫苗-->
有些病毒性的性傳播疾病有對應的疫苗，例如B型肝炎疫苗及針對某些乳突病毒的人類乳突病毒疫苗，若要達到最大的保護效果，需要在初次性接觸前就施打疫苗。
<!--保險套-->
保險套及女用保險套若正常使用時，可以形成一些病毒或細菌的障礙，但只保護保險套以內的部份，沒被保險套遮蓋住的部份仍有可能得到性傳播疾病。
以HIV病毒為例，性傳播的路徑幾乎都包括陰莖，因為HIV病毒無法穿過無傷口的皮膚，若在陰莖上以正確方式穿戴保險套，在進行陰道性交或是且肛交都可以有效的避免HIV病毒的傳播。若皮膚有傷口，接觸到患者的體液，有可能讓HIV病毒傳播，此情形一般不算是「性傳播」，但在性接觸時仍然可能發生，在有流血傷口時不進行性接觸，即可避免此一情形。
其他的性傳播疾病（甚至包括病毒感染）可以藉由使用乳膠、聚氨酯或聚異戊二烯的保險套來作為阻隔。有些微生物或病毒很小，可以穿過自然材質的保險套，但仍無法穿過乳膠或是合成橡膠類的保險套。
正確的使用方式包括：
為了會避免性傳播疾病，用過的保險套及其內容物均需視為有傳染性的，因此需以適當的方式丟棄。
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壬苯醇醚-9是一種陰道用的殺微生物藥及殺精劑，一些研究者原希望壬苯醇醚-9可以減少感染性傳播疾病的風險，不過後來發現沒有效果[9]，而且可能讓女性受到HIV感染的風險更高[10]。
雖然性傳播疾病的診斷及治療都有許多進步，許多病患都可以治療到不具感染力，甚至治癒，但性傳播疾病的罹患比率仍在持續上昇，在許多文化中，性道德的改變且口服避孕藥的出現造成性行為已不會受到傳統一樣的限制（尤其對女性更是如此），而醫生和病人也很難公開及坦誠的處理性方面的議題。而且抗藥性細菌（如抗盤尼西林的淋球菌）的出現及擴散也使性傳播疾病更難治療。1970年代愛滋病病毒（HIV-1）從非洲及歐洲快速擴散到美洲，旅行是其中一個主要原因[12]。
在性行為活躍的少女中（不考慮是否有生殖道症狀），常見的性傳播疾病有衣原體感染（10-25%）、淋病（3–18%）、梅毒（0–3%）、滴蟲（8–16%）及單純皰疹病毒（2–12%）。性行為活躍的少年，且沒有尿道炎症狀的，常見的性傳播疾病有衣原體（9–11%）及淋病（2–3%）。2008年美國疾病控制與預防中心的研究指出美國的少女中，有25–40%有性傳播疾病[13][14]。
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*11/04已整合到中文維基性感染疾病條目
