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Human Immunodeficiency Virus (view source)

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The '''Human Immunodeficiency Virus (HIV)''' is a chronic disease that gradually weakens the immune system by disabling and killing "T-helper ", which normally signal other constituents of the immune system to perform their respective roles. When HIV reduces the number of T-helper cells below a certain threshold, an infected person is vulnerable to opportunistic infections and cancers that typify Acquired ImmunoDeficiency Syndrome, or AIDS. <ref>[http://www.niaid.nih.gov/factsheets/howhiv.htm]</ref> It is transmitted primarily through sexual contact with an infected person, sharing of needles or syringes, and, less frequently, through transfusion of infected blood or blood clotting factors. <ref>[http://www.cdc.gov/hiv/resources/factsheets/transmission.htm]</ref>. 
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The '''Human Immunodeficiency Virus (HIV)''' is a chronic disease that gradually weakens the immune system by disabling and killing "T-helper ", which normally signal other constituents of the immune system to perform their respective roles. When HIV reduces the number of T-helper cells below a certain threshold, an infected person is vulnerable to opportunistic infections and cancers that typify Acquired ImmunoDeficiency Syndrome, or AIDS. <ref>[http://www.niaid.nih.gov/factsheets/howhiv.htm]</ref>
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==Transmission==
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:''For more details on this topic, see [[AIDS#Transmission and prevention|AIDS transmission and prevention]]
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{| class="prettytable" style="float:right; font-size:85%; margin-left:15px;"
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|- bgcolor="#efefef"
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! colspan=5 style="border-right:0px;";| Estimated per act risk for acquisition of HIV-1 <br />by exposure route<ref name=MMWR>{{cite journal | author=Smith, D. K., Grohskopf, L. A., Black, R. J., Auerbach, J. D., Veronese, F., Struble, K. A., Cheever, L., Johnson, M., Paxton, L. A., Onorato, I. A. and Greenberg, A. E. | title=Antiretroviral Postexposure Prophylaxis After Sexual, Injection-Drug Use, or Other Nonoccupational Exposure to HIV in the United States | journal=MMWR | year=2005 | pages=1-20 | volume=54 | issue=RR02 | url=http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5402a1.htm}}</ref>
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|- bgcolor="#efefef"
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| style="width: 100px"|'''Exposure Route'''
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| align="center" style="width: 150px"|'''Estimated infections per 10,000 exposures to an infected source'''
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|-
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| Blood Transfusion
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| align="center" | 9,000<ref name=Donegan>{{cite journal
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| author=Donegan, E., Stuart, M., Niland, J. C., Sacks, H. S., Azen, S. P., Dietrich, S. L., Faucett, C., Fletcher, M. A., Kleinman, S. H., Operskalski, E. A., et al.
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| title=Infection with human immunodeficiency virus type 1 (HIV-1) among recipients of antibody-positive blood donations
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| journal=Ann. Intern. Med.
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| year=1990
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| pages=733-739
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| volume=113
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| issue=10
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| id= PMID 2240875
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}}</ref>
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|-
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| Childbirth
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| align="center" | 2,500<ref name=Coovadia>{{cite journal
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| author=Coovadia, H.
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| title=Antiretroviral agents&mdash;how best to protect infants from HIV and save their mothers from AIDS | journal=N. Engl. J. Med.
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| year=2004
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| pages=289-292
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| volume=351
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| issue=3
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| id= PMID 15247337
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| format=
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}}</ref>
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|-
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| Needle-sharing injection drug use
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| align="center" | 67<ref name=Kaplan>{{cite journal | author=Kaplan, E. H. and Heimer, R. | title=HIV incidence among New Haven needle exchange participants: updated estimates from syringe tracking and testing data | journal=J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. | year=1995 | pages=175-176 | volume=10 | issue=2
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| id= PMID 7552482 }}</ref>
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|-
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| Receptive anal intercourse<sup>*</sup>
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| align="center" | 50<ref name=ESG>{{cite journal | author=European Study Group on Heterosexual Transmission of HIV | title=Comparison of female to male and male to female transmission of HIV in 563 stable couples | journal=BMJ. | year=1992 | pages=809-813 | volume=304 | issue=6830 | id= PMID 1392708 |format=}}</ref><ref name=Varghese>{{cite journal | author=Varghese, B., Maher, J. E., Peterman, T. A., Branson, B. M. and Steketee, R. W. | title=Reducing the risk of sexual HIV transmission: quantifying the per-act risk for HIV on the basis of choice of partner, sex act, and condom use | journal=Sex. Transm. Dis. | year=2002 | pages=38-43 | volume=29 | issue=1 | id= PMID 11773877 |format=}}</ref>
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|-
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| Percutaneous needle stick
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| align="center" | 30<ref name=Bell>{{
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cite journal | author=Bell, D. M. | title=Occupational risk of human immunodeficiency virus infection in healthcare workers: an overview. | journal=Am. J. Med. | year=1997 | pages=9-15 | volume=102 | issue=5B | id= PMID 9845490
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}}</ref>
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|-
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| Receptive penile-vaginal intercourse<sup>*</sup>
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| align="center" | 10<ref name=ESG /><ref name=Varghese /><ref name=Leynaert>{{
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cite journal | author=Leynaert, B., Downs, A. M. and de Vincenzi, I. | title=Heterosexual transmission of human immunodeficiency virus: variability of infectivity throughout the course of infection. European Study Group on Heterosexual Transmission of HIV | journal=Am. J. Epidemiol. | year=1998 | pages=88-96 | volume=148 | issue=1 | id= PMID 9663408
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}}</ref>
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|-
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| Insertive anal intercourse<sup>*</sup>
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| align="center" | 6.5<ref name=ESG /><ref name=Varghese />
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|-
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| Insertive penile-vaginal intercourse<sup>*</sup>
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| align="center" | 5<ref name=ESG /><ref name=Varghese />
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|-
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| Receptive fellatio<sup>*</sup>
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| align="center" | 1<ref name=Varghese />
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|-
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| Insertive fellatio<sup>*</sup>
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| align="center" | 0.5<ref name=Varghese />
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|- bgcolor="#efefef"
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! colspan=5 style="border-right:0px;";| <sup>*</sup> assuming no condom use </br>
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|}
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Since the beginning of the [[pandemic]], three main transmission routes for HIV have been identified:
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*'''Sexual route.''' The majority of HIV infections are acquired through unprotected sexual relations. Sexual transmission can occur when infected sexual secretions of one partner come into contact with the rectal, genital or oral [[mucous membranes]] of another.
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*'''Blood or blood product route.''' This transmission route can account for infections in intravenous drug users, [[hemophiliac]]s and recipients of [[blood transfusion]]s (though most transfusions are checked for HIV in the developed world) and blood products. It is also of concern for persons receiving medical care in regions where there is prevalent substandard hygiene in the use of injection equipment, such as the reuse of needles in Third World countries. HIV can also be spread through the sharing of leaches. Health care workers such as nurses, laboratory workers, and doctors, have also been infected, although this occurs more rarely. People who give and receive tattoos, piercings and scarification procedures can also be at risk of infection.
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*'''Mother-to-child transmission''' (MTCT). The transmission of the virus from the mother to the child can occur ''in utero'' during the last weeks of pregnancy and at childbirth. In the absence of treatment, the transmission rate between the mother and child is 25%.<ref name=Coovadia /> However, where drug treatment and [[Cesarian section]] are available, this can be reduced to 1%.<ref name=Coovadia /> Breast feeding also presents a risk of infection for the baby.
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HIV-2 is transmitted much less frequently by the MTCT and sexual route than HIV-1.
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HIV has been found at low concentrations in the [[saliva]], [[tears]] and [[urine]] of infected individuals, but there are no recorded cases of infection by these secretions and the potential risk of transmission is negligible. The use of physical barriers such as the [[latex]] [[condom]] is widely advocated to reduce the sexual transmission of HIV. [[Spermicide]], when used alone or with vaginal contraceptives like a [[diaphragm (contraceptive)|diaphragm]], actually increases the male to female transmission rate due to inflammation of the vagina; it should not be considered a barrier to infection.<ref name="spermicide">{{cite web |url=http://www.fda.gov/oashi/aids/condom.html#should |title=Should spermicides be used with condoms? |accessdate=2006-10-23 |work=Condom Brochure, FDA OSHI HIV STDs }}</ref> Research is clarifying the relationship between male [[circumcision]] and HIV in differing social and cultural contexts, however critics point out that any correlation between circumcision and HIV is likely to come from cultural factors (which govern not only whether someone is circumcised, but also their sexual practices and beliefs).<ref name=Siegfred>
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{{cite journal
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| author=Siegfried, N., Muller, M., Deeks, J., Volmink, J., Egger, M., Low, N., Walker, S. and Williamson, P. | title=HIV and male circumcision--a systematic review with assessment of the quality of studies | journal=Lancet Infect. Dis. | year=2005 | pages=165-173 | volume=5 | issue=3 | id= PMID 15766651
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}}</ref> Even though male circumcision may lead to a reduction of infection risk in heterosexual men by up to 60%,<ref name=Williams>{{
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cite journal
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| author=Williams BG, Lloyd-Smith JO, Gouws E, Hankins C, Getz WM, Hargrove J, de Zoysa I, Dye C, Auvert B.
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| title=The Potential Impact of Male Circumcision on HIV in Sub-Saharan Africa.
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| journal=PLoS Med  | year=2006 | pages=e262 | volume=3 | issue=7
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| id= PMID 16822094
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}}</ref> UNAIDS believes that it is premature to recommend male circumcision as part of HIV prevention programs.<ref name=WHOcircumcision>{{
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cite web
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| author=[[WHO]] | publisher= | year=2005
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| url=http://www.who.int/mediacentre/news/releases/2005/pr32/en/
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| title=UNAIDS statement on South African trial findings regarding male circumcision and HIV
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| accessdate=2006-03-28
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}}</ref> Trials, in which some uncircumcised men were randomly assigned to be circumcised in presumably sterile conditions and others were not circumcised, conducted in Kenya[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&cmd=Retrieve&dopt=abstractplus&list_uids=17321310] and Uganda [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&cmd=Retrieve&dopt=abstractplus&list_uids=17321311] found that men who were uncircumcised were twice as likely to contract the human immunodeficiency virus (HIV) compared with circumcised counterparts. South African medical experts are concerned that the repeated use of unsterilized blades in the ritual circumcision of adolescent boys may be spreading HIV.<ref name=Kaisercircum>{{
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cite web
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| author=Various | publisher=Kaisernetwork.org | year=2005
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| url=http://www.kaisernetwork.org/daily_reports/rep_index.cfm?DR_ID=31199
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| title=Repeated Use of Unsterilized Blades in Ritual Circumcision Might Contribute to HIV Spread in S. Africa, Doctors Say
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| accessdate=2006-03-28
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}}</ref>
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==Treatment==
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==Replication Cycle==
 
HIV is a retrovirus, and integrates its genetic information into the host cell's genome.
 
HIV is a retrovirus, and integrates its genetic information into the host cell's genome.
    
==References==
 
==References==
 
<references/>
 
<references/>
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==License==
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This article contains material from [[Wikipedia]] licensed under the [[GFDL]].
MikeA
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