HIV的傳播與預防

1. Transmission

HIV transmission requires contact with body fluids containing infected cells or plasma. HIV may be present in any fluid or exudate that contains plasma or lymphocytes, specifically blood, semen, vaginal secretions, breast milk, saliva, or wound exudates. Although theoretically possible, transmission by saliva or droplet nuclei produced by coughing or sneezing is extremely rare, if it occurs. HIV is not transmitted by casual contact or even by the close nonsexual contact that occurs at work, school, or home. The most common means of transmission is direct transfer of bodily fluids either through sharing contaminated needles or sexual relations.

傳播

　　HIV的傳播必需要有與含感染細胞或血漿體液的直接接觸。HIV可存在于任何含血漿或淋巴細胞的液體或滲出液中，特別是血液、精液、陰道分泌液、母乳、唾液或傷口滲出液。雖然從理論上講有這種可能性，但在實際中，通過咳嗽或噴嚏唾液或飛沫傳播的情形極其罕見。在工作場所、學�；蚣依锏钠匠＝佑|甚或密切的非性接觸都不會傳播HIV。最覺見的傳播途徑是共用注射器或性關系所帶來的直接的全液交流。

Sexual practices involving no exposure to bodily fluids are safe. Other practices, such as fellatio and cunnilingus appear to be relatively, but not absolutely, safe. The greatest risk is through genital intercourse, especially anal-receptive intercourse. Sexual practices producing mucosal trauma before or during intercourse increase the risk. Use of latex condoms or vaginal barriers decreases but does not eliminate risk. Oil-based lubricants decrease the protection provided by latex condoms because they dissolve them.

無體液接觸的性生活是安全的。其他如口yin或舐陰等性方式則相對而非絕對安全。最危險的是生殖器性交，尤其是肛交的接受方。性交前或性交中的粘膜破損會增加危險性。使用乳膠避孕套或子宮帽可降低但不能消除這種危險。因為潤滑油會溶解乳膠，所以，也會降低避孕套的保護作用.

Infected cells or free virions can reach target cells in a new host via blood transfusion, accidental injection, or mucous membrane exposure. The role of mucous membrane inflammation is illustrated by the effect of other sexually transmitted diseases (STDs) on susceptibility to HIV infection. HIV transmission is definitely increased by chancroid and may be more likely in the presence of herpes, syphilis, trichomoniasis, and possibly other STDs.

感染細胞或游離病毒體可經由輸血、意外注射或粘膜暴露到達新宿主的靶細胞。粘膜炎癥所起的作用與其他性傳病(STD)和HIV感染易感性的作用相同。軟下疳肯定會增加HIV的傳播性，單純皰疹、梅毒、滴蟲病和其他STD感染更可能引發(fā)HIV傳播。

Transmission of HIV by needle-stick injury, estimated at about 1/300 incidents, is much less frequent than transmission of hepatitis B, presumably because of the relatively lower number of HIV virions in the blood of most infected patients. Risk of HIV transmission appears to be increased by deep wounds or injection of blood, such as when hollow-bore needles containing blood penetrate the skin.

由針刺損傷導致的HIV傳播發(fā)生率估計為1/300，遠低于乙型肝炎，這可能是由于大多數(shù)感染者血液中的HIV病毒數(shù)量相對較少的原故。深部創(chuàng)口或注入血液，如含有血液的中空針頭刺入皮膚，都可增加HIV的傳播危險。

Use of enzyme-linked immunosorbent assay (ELISA) to screen blood donors has vastly reduced the risk of acquiring HIV by transfusion. However, persons in the early stages of HIV infection, who have not yet mounted an antibody response, may have transiently negative ELISA and Western blot results while yielding positive results for HIV p24 antigen in plasma. These persons may account for the very low, but continuing, risk of transfusion-associated HIV infection (estimated at between 1/10,000 and 1/100,000 per unit transfused). Currently mandated screening for both antibody and p24 antigen may further reduce this risk.醫(yī)學.全在線www.med126.com

用酶聯(lián)免疫吸附試驗(ELISA)方法對供血者進行篩檢，已大大降低了輸血引起的HIV感染危險。不過，HIV感染早期的供血者，在尚未產生抗體應答時，他們的ELISA和Westernblot結果暫時均為陰性，而血漿HIVp24抗原檢查則為陽性。這些供血者可能造成非常低、但依然存在的輸血相關性HIV感染危險(估計介于1/1萬~1/10萬之間)。近來采用同時進行抗體和p24抗原篩檢的方法可進一步降低危險性。

2. Prevention

Multiple strategies are being developed to induce protective immunity in persons not infected with HIV. Immunogens include attenuated live and whole killed HIV, genetically engineered HIV proteins and peptides (e.g., from the viral envelope), and vaccinia virus genetically modified to express HIV viral proteins. These efforts are hampered by the lack of a measurable marker of protective immunity, such as the neutralizing antibody engendered by polio vaccine, or of a convenient animal model. Nevertheless, vaccines continue to be developed and tested for safety and immunogenicity.

傳播的預防

　　正在研制多種方法來誘導未感染HIV者的免疫保護功能。免疫原包括減毒HIV活病毒或完全滅活HIV病毒，因工程HIV蛋白和肽（如取自病毒包膜的)，和基因修飾后表達HIV蛋白質的牛痘病毒。這些工作都因缺少可計量的免疫保護標志物而受阻，如灰髓炎疫苗能產生中和抗體；另外也沒有合適的動物模型。盡管如此，疫苗研究仍在進行。并在作安全性和免疫遺傳學試驗。

All pregnant women should be offered a test for antibody to HIV. HIV-infected women should be advised to consider deferring pregnancy at least until management of HIV in pregnancy is better studied. The risk of transmission in utero, intrapartum, or postpartum transmission to the fetus is estimated to be 30 to 50%, but zidovudine (ZDV or AZT) alone reduces intrapartum infection by 2/3, and combinations of drugs may be more effective. Given the low, but real, risk of transmission even with treatment and the uncertainty of the effects on the fetus of drugs needed for their own health, termination of pregnancy may be an alternative for many HIV-infected pregnant women.

所有妊娠婦女都應進行HIV抗體試驗。應勸告HIV感染女性推遲懷孕，至少要等到妊娠期HIV處理已有了更好的研究結果后。據(jù)估計，胎兒在宮內、產程中或產后的傳播危險率為30%~50%，但單用齊多呋啶（ZDV或AZT)即可使分娩期傳播減少2/3，聯(lián)合用藥效果會更好。雖然治療后的傳播危險很低，但也確實存在，而且這些胎兒健康所必需的藥物對胎兒的影響也不確定，因此，終止妊娠也可能是許多HIV感染孕婦的選擇措施之一。

Confidential testing for antibody to HIV should be offered to anyone requesting it, but only in conjunction with pretest and posttest counseling. Persons who are at high risk for contracting HIV infection--even those with negative HIV antibody test results--should not donate blood or organs for transplantation because of the small risk they may have been recently infected and be infectious but antibody-negative.

應向每一個請求者提供保密的HIV抗體檢測，并與檢測前后的咨詢服務相結合。HIV感染高危者――即使是那些HIV抗體檢測陰性的人――都不應獻血或捐獻移植器官，因為他們仍然存在近期感染及具有傳染性而抗體呈陰性的可能性。

Isolation of hospitalized patients with HIV infection is unnecessary, except when their complicating infections (e.g., suspected or proven TB) are communicable. Surfaces contaminated by blood or other body fluids should be cleaned and disinfected. HIV is readily inactivated by heat and many disinfectants, including peroxide, alcohols, phenolics, and hypochlorite. The body fluids and tissues of HIV-infected patients should be handled with extreme care.醫(yī)學全在.線gydjdsj.org.cn

沒必要隔離感染HIV的住院病人，除非他們得有傳染性并發(fā)感染（如懷疑或證實有結核)。血液或其他體液污染表面應進行清潔和消毒。HIV容易通過加熱和許多消毒劑滅活，如過氧化物、酒精、酚和次氯酸。處理HIV感染者的體液和組織時應極其小心。

Medical and dental professionals should wear gloves when examining all patients if contact with mucous membranes or other wet surfaces may occur. Because needle-stick accidents are common, health care workers must be taught how to avoid them.

醫(yī)生和牙醫(yī)在檢查所有患者時，如需接觸粘膜或其他濕面，一定要戴手套。由于針刺意外經常發(fā)生，因此，應教育保健工作者如何避免意外。

Postexposure prophylaxis with immediate antiretroviral therapy after penetrating injuries involving HIV-infected blood (needle sticks) or heavy mucous membrane (eye or mouth) contamination is believed to reduce transmission. Combinations of a protease inhibitor with two nucleoside reverse transcriptase inhibitors are currently recommended for postexposure prophylaxis of relatively high-risk exposures. Zidovudine (ZDV or AZT) appeared to reduce risk of transmission after needle-stick injuries in one study, which provided the only evidence that prophylaxis works. Because of the low risk of infection for most injuries, controlled prospective studies of the effectiveness of prophylaxis are not practical. Cancers or birth defects from the brief exposures to these drugs have not been found in the small numbers of otherwise healthy persons who have used ZDV for this purpose. Because some women in early pregnancy will be offered postexposure prophylaxis before their pregnancy is suspected or confirmed, special caution must be exercised in treating potentially pregnant women. Additional problems arise when the source or HIV status of blood is unknown, but identification of the source and testing of that person for HIV infection should be vigorously pursued.

現(xiàn)已證明，在貫通傷接觸HIV感染血液或嚴重的粘膜（口腔或眼睛)接觸后，立即用抗逆轉錄病毒藥物作暴露后預防治療可以能降低傳播率。對相對高危暴露，目前推薦用一個蛋白酶抑制劑結合兩個逆轉錄酶抑制劑作暴露后預防治療。有一項研究發(fā)現(xiàn)，AZT能降低針刺后的傳播危險，――這也是證明預防有效的唯一一次研究。由于大多數(shù)針刺的感染危險性低，預防效果的預期控制性研究也并不實用。在其他不部分HIV感染而使用ZDV、又無其他疾病的人員中，尚未發(fā)現(xiàn)短期用藥的致癌和致畸現(xiàn)象。因此，有些妊娠早期婦女在懷疑或證實懷孕前需要進行預防性治療，在治療這些潛在的孕婦時就應特別注意。血液來源或血液HIV狀況不明會引發(fā)其他許多問題，因此確認血液來源及對供血者進行HIV檢測絲毫不能松懈。