高中英语人教版Unit3AHealthyLife 高二unit3素材3

AIDSAcquiredimmunodeficiencysyndrome(AIDS)

ClassificationandexternalresourcesTheisasymbolforsolidaritywithHIV-positivepeopleandthoselivingwithAIDS.--

ListofabbreviationsusedinthisarticleAIDS:Acquiredimmunedeficiencysyndrome

HIV:

CD4+:

CCR5:

CDC:

WHO:

PCP:

TB:

MTCT:Mother-to-childtransmission

HAART:

STI/STD:/diseaseAcquiredimmunedeficiencysyndromeoracquiredimmunodeficiencysyndrome(AIDS)isadiseaseofthehumancausedbythe(HIV).Thisconditionprogressivelyreducestheeffectivenessoftheimmunesystemandleavesindividualssusceptibletoand.HIVisthroughdirectcontactofaorthebloodstreamwithacontainingHIV,suchas,,,,and.Thistransmissioncaninvolve,or,,contaminated,exchangebetweenmotherandbabyduring,,or,orotherexposuretooneoftheabovebodilyfluids.AIDSisnowa.In2023,itwasestimatedthat

millionpeoplelivedwiththediseaseworldwide,andthatAIDShadkilledanestimated

millionpeople,including330,000children.Overthree-quartersofthesedeathsoccurredin,retardinganddestroying.indicatesthatHIVoriginatedinwest-centralAfricaduringthelatenineteenthorearlytwentiethcentury.AIDSwasfirstrecognizedbythe.in1981anditscause,HIV,identifiedintheearly1980s.AlthoughtreatmentsforAIDSandHIVcanslowthecourseofthedisease,thereiscurrentlynovaccineorcure.treatmentreducesboththeandthemorbidityofHIVinfection,butthesedrugsareexpensiveandroutineaccesstoantiretroviralisnotavailableinallcountries.DuetothedifficultyintreatingHIVinfection,preventinginfectionisakeyaimincontrollingtheAIDSepidemic,withhealthorganizationspromotingandinattemptstoslowthespreadofthevirus.SymptomsAgeneralizedgraphoftherelationshipbetweenHIVcopies(viralload)andCD4countsovertheaveragecourseofuntreatedHIVinfection;anyparticularindividual'sdiseasecoursemayvaryconsiderably.CD4+TLymphocytecount(cells/mm³)HIVRNAcopiespermLofplasmaThesymptomsofAIDSareprimarilytheresultofconditionsthatdonotnormallydevelopinindividualswithhealthy.Mostoftheseconditionsareinfectionscausedby,,andthatarenormallycontrolledbytheelementsoftheimmunesystemthatHIVdamages.arecommoninpeoplewithAIDS.HIVaffectsnearlyevery.PeoplewithAIDSalsohaveanincreasedriskofdevelopingvariouscancerssuchas,andcancersoftheimmunesystemknownas.Additionally,peoplewithAIDSoftenhavesystemicsymptomsofinfectionlike,(particularlyatnight),swollenglands,chills,weakness,and.ThespecificopportunisticinfectionsthatAIDSpatientsdevelopdependinpartontheprevalenceoftheseinfectionsinthegeographicareainwhichthepatientlives.MainsymptomsofAIDS.PulmonaryinfectionsX-rayof.Thereisincreasedwhite(opacity)inthelowerlungsonbothsides,characteristicofPCP(originallyknownasPneumocystiscariniipneumonia,andstillabbreviatedasPCP,whichnowstandsforPneumocystispneumonia)isrelativelyrareinhealthy,people,butcommonamongHIV-infectedindividuals.Itiscausedby.Beforetheadventofeffectivediagnosis,treatmentandroutineinWesterncountries,itwasacommonimmediatecauseofdeath.Indevelopingcountries,itisstilloneofthefirstindicationsofAIDSinuntestedindividuals,althoughitdoesnotgenerallyoccurunlesstheCD4countislessthan200cellsperµLofblood.(TB)isuniqueamonginfectionsassociatedwithHIVbecauseitistransmissibletoimmunocompetentpeopleviatherespiratoryroute,iseasilytreatableonceidentified,mayoccurinearly-stageHIVdisease,andispreventablewithdrugtherapy.However,isapotentiallyseriousproblem.EventhoughitsincidencehasdeclinedbecauseoftheuseofdirectlyobservedtherapyandotherimprovedpracticesinWesterncountries,thisisnotthecaseindevelopingcountrieswhereHIVismostprevalent.Inearly-stageHIVinfection(CD4count>300cellsperµL),TBtypicallypresentsasapulmonarydisease.InadvancedHIVinfection,TBoftenpresentsatypicallywithextrapulmonary(systemic)diseaseacommonfeature.Symptomsareusuallyconstitutionalandarenotlocalizedtooneparticularsite,oftenaffecting,,urinaryand,,regional,andthe.Gastrointestinalinfectionsisaninflammationoftheliningofthelowerendofthe(gulletorswallowingtubeleadingtothe).InHIVinfectedindividuals,thisisnormallyduetofungal()orviral(or)infections.Inrarecases,itcouldbedueto.UnexplainedchronicinHIVinfectionisduetomanypossiblecauses,includingcommonbacterial(,,or)andparasiticinfections;anduncommonopportunisticinfectionssuchas,,complex(MAC)andviruses,,,and,(thelatterasacourseof).Insomecases,diarrheamaybeasideeffectofseveraldrugsusedtotreatHIV,oritmaysimplyaccompanyHIVinfection,particularlyduringprimaryHIVinfection.Itmayalsobeasideeffectofusedtotreatbacterialcausesofdiarrhea(commonfor).InthelaterstagesofHIVinfection,diarrheaisthoughttobeareflectionofchangesinthewaytheabsorbsnutrients,andmaybeanimportantcomponentofHIV-related.NeurologicalandpsychiatricinvolvementHIVinfectionmayleadtoavarietyofneuropsychiatric,eitherbyinfectionofthenowsusceptiblenervoussystembyorganisms,orasadirectconsequenceoftheillnessitself.isadiseasecausedbythesingle-celledcalledToxoplasmagondii;itusuallyinfectsthebrain,causingtoxoplasma,butitcanalsoinfectandcausediseaseintheandlungs.Cryptococcalmeningitisisaninfectionofthe(themembranecoveringthebrainand)bythefungus.Itcancausefevers,,,,and.Patientsmayalsodevelopandconfusion;leftuntreated,itcanbelethal.(PML)isa,inwhichthegradualdestructionofthesheathcoveringtheofnervecellsimpairsthetransmissionofnerveimpulses.Itiscausedbyaviruscalledwhichoccursin70%ofthepopulationinform,causingdiseaseonlywhentheimmunesystemhasbeenseverelyweakened,asisthecaseforAIDSpatients.Itprogressesrapidly,usuallycausingdeathwithinmonthsofdiagnosis.(ADC)isametabolicinducedbyHIVinfectionandfueledbyimmuneactivationofHIVinfectedbrainand.ThesecellsareproductivelyinfectedbyHIVandsecreteofbothhostandviralorigin.Specificneurologicalimpairmentsaremanifestedbycognitive,behavioral,andmotorabnormalitiesthatoccurafteryearsofHIVinfectionandareassociatedwithlowCD4+Tcelllevelsandhighplasmaviralloads.Prevalenceis10–20%inWesterncountriesbutonly1–2%ofHIVinfectionsinIndia.ThisdifferenceispossiblyduetotheHIVsubtypeinIndia.AIDSrelatedmaniaissometimesseeninpatientswithadvancedHIVillness;itpresentswithmoreirritabilityandcognitiveimpairmentandlesseuphoriathanaassociatedwithtrue.Unlikethelattercondition,itmayhaveamorechroniccourse.Thissyndromeislessoftenseenwiththeadventofmulti-drugtherapy.TumorsandmalignanciesPatientswithHIVinfectionhavesubstantiallyincreasedincidenceofseveral.Thisisprimarilyduetoco-infectionwithan,especially(EBV),(KSHV),andhuman(HPV).Kaposi'ssarcoma(KS)isthemostcommontumorinHIV-infectedpatients.Theappearanceofthistumorinyounghomosexualmenin1981wasoneofthefirstsignalsoftheAIDSepidemic.Causedbyaviruscalled(KSHV),itoftenappearsaspurplishontheskin,butcanaffectotherorgans,especiallythe,gastrointestinaltract,andlungs.High-gradesuchas,Burkitt's-likelymphoma,diffuselargeB-celllymphoma(DLBCL),andpresentmoreofteninHIV-infectedpatients.Theseparticularcancersoftenforeshadowapoorprognosis.InsomecasestheselymphomasareAIDS-defining.(EBV)orKSHVcausemanyoftheselymphomas.inHIV-infectedwomenisconsideredAIDS-defining.Itiscausedby(HPV).InadditiontotheAIDS-definingtumorslistedabove,HIV-infectedpatientsareatincreasedriskofcertainothertumors,suchasandand.However,theincidenceofmanycommontumors,suchasor,doesnotincreaseinHIV-infectedpatients.InareaswhereisextensivelyusedtotreatAIDS,theincidenceofmanyAIDS-relatedmalignancieshasdecreased,butatthesametimemalignantcancersoverallhavebecomethemostcommoncauseofdeathofHIV-infectedpatients.OtheropportunisticinfectionsAIDSpatientsoftendevelopopportunisticinfectionsthatpresentwithnon-specificsymptoms,especiallyandweightloss.Theseincludeinfectionwith-intracellulareand(CMV).CMVcancausecolitis,asdescribedabove,andcancause.duetoisnowthethirdmostcommonopportunisticinfection(afterextrapulmonarytuberculosisand)inHIV-positiveindividualswithintheendemicareaof.CauseFormoredetailsonthistopic,see.ofHIV-1,coloredgreen,buddingfromacultured.AIDSisthemostsevereaccelerationofwithHIV.HIVisathatprimarilyinfectsvitalorgansofthehumansuchas(asubsetof),and.ItdirectlyandindirectlydestroysCD4+Tcells.OnceHIVhaskilledsomanyCD4+Tcellsthattherearefewerthan200ofthesecellsper(µL)of,islost.HIVinfectionprogressesovertimetoclinicallatentHIVinfectionandthentoearlyHIVinfectionandlatertoAIDS,whichisidentifiedeitheronthebasisoftheamountofCD4+Tcellsremainingintheblood,and/orthepresenceofcertaininfections,asnotedabove.Intheabsenceof,theisninetotenyears,andthemediansurvivaltimeafterdevelopingAIDSisonlymonths.However,therateofclinicaldiseaseprogressionvarieswidelybetweenindividuals,fromtwoweeksupto20

years.Manyfactorsaffecttherateofprogression.Theseincludefactorsthatinfluencethebody'sabilitytodefendagainstHIVsuchastheinfectedperson'sgeneralimmunefunction.Olderpeoplehaveweakerimmunesystems,andthereforehaveagreaterriskofrapiddiseaseprogressionthanyoungerpeople.Pooraccesstoandtheexistenceofcoexistinginfectionssuchasalsomaypredisposepeopletofasterdiseaseprogression.Theinfectedperson'splaysanimportantroleandsomepeoplearetocertainstrainsofHIV.AnexampleofthisispeoplewiththevariationareresistanttoinfectionwithcertainofHIV.HIVisgeneticallyvariableandexistsasdifferentstrains,whichcausedifferentratesofclinicaldiseaseprogression.SexualtransmissionSexualtransmissionoccurswiththecontactbetweensexualsecretionsofonepersonwiththerectal,genitalororalofanother.Unprotectedreceptivesexualactsareriskierthanunprotectedinsertivesexualacts,andtheriskfortransmittingHIVthroughunprotectedanalintercourseisgreaterthantheriskfromvaginalintercourseororalsex.However,oralsexisnotentirelysafe,asHIVcanbetransmittedthroughbothinsertiveandreceptiveoralsex.greatlyincreasestheriskofHIVtransmissionascondomsarerarelyemployedandphysicaltraumatothevaginaoccursfrequently,facilitatingthetransmissionofHIV.Other(STI)increasetheriskofHIVtransmissionandinfection,becausetheycausethedisruptionofthenormalbarrierbyand/ormicroulceration;andbyaccumulationofpoolsofHIV-susceptibleorHIV-infectedcells(and)insemenandvaginalsecretions.Epidemiologicalstudiesfromsub-SaharanAfrica,andsuggestthatgenitalulcers,suchasthosecausedbyand/or,increasetheriskofbecominginfectedwithHIVbyaboutfourfold.ThereisalsoasignificantalthoughlesserincreaseinriskfromSTIssuchas,and,whichallcauselocalaccumulationsoflymphocytesandmacrophages.TransmissionofHIVdependsontheinfectiousnessoftheandthesusceptibilityoftheuninfectedpartner.Infectivityseemstovaryduringthecourseofillnessandisnotconstantbetweenindividuals.Anundetectableplasmadoesnotnecessarilyindicatealowviralloadintheseminalliquidorgenitalsecretions.However,each10-foldincreaseinthelevelofHIVinthebloodisassociatedwithan81%increasedrateofHIVtransmission.WomenaremoresusceptibletoHIV-1infectionduetohormonalchanges,vaginalmicrobialecologyandphysiology,andahigherprevalenceofsexuallytransmitteddiseases.PeoplewhohavebeeninfectedwithonestrainofHIVcanstillbeinfectedlateronintheirlivesbyother,morestrains.Infectionisunlikelyinasingleencounter.Highratesofinfectionhavebeenlinkedtoapatternofoverlappinglong-termsexualrelationships.Thisallowsthevirustoquicklyspreadtomultiplepartnerswhointurninfecttheirpartners.Apatternofserialmonogamyoroccasionalcasualencountersisassociatedwithlowerratesofinfection.HIVspreadsreadilythroughheterosexualsexinAfrica,butlesssoelsewhere.Onepossibilitybeingresearchedisthat,whichaffectsupto50percentofwomeninpartsofAfrica,damagestheliningofthevagina.Exposuretoblood-bornepathogensCDCposterfrom1989highlightingthethreatofAIDSassociatedwithdruguseThistransmissionrouteisparticularlyrelevanttousers,andrecipientsofandbloodproducts.SharingandreusingcontaminatedwithHIV-infectedbloodrepresentsamajorriskforinfectionwithHIV.NeedlesharingisthecauseofonethirdofallnewHIV-infectionsin,China,and.TheriskofbeinginfectedwithHIVfromasingleprickwithaneedlethathasbeenusedonanHIV-infectedpersonisthoughttobeabout1in150().withanti-HIVdrugscanfurtherreducethisrisk.Thisroutecanalsoaffectpeoplewhogiveandreceiveand.arefrequentlynotfollowedinbothsub-SaharanAfricaandmuchofAsiabecauseofbothashortageofsuppliesandinadequatetraining.Theestimatesthatapproximately%ofallHIVinfectionsinsub-SaharanAfricaaretransmittedthroughunsafehealthcareinjections.Becauseofthis,thehasurgedthenationsoftheworldtoimplementprecautionstopreventHIVtransmissionbyhealthworkers.TheriskoftransmittingHIVtorecipientsisextremelylowindevelopedcountrieswhereimproveddonorselectionandHIVscreeningisperformed.However,accordingtothe,theoverwhelmingmajorityoftheworld'spopulationdoesnothaveaccesstosafebloodandbetween5%and10%oftheworld'sHIVinfectionscomefromtransfusionofinfectedbloodandbloodproducts.PerinataltransmissionThetransmissionofthevirusfromthemothertothechildcanoccurduringthelastweeksofpregnancyandatchildbirth.Intheabsenceoftreatment,thetransmissionratebetweenamotherandherchildduringpregnancy,laboranddeliveryis25%.However,whenthemothertakesantiretroviraltherapyandgivesbirthby,therateoftransmissionisjust1%.Theriskofinfectionisinfluencedbytheviralloadofthemotheratbirth,withthehighertheviralload,thehighertherisk.alsoincreasestheriskoftransmissionbyabout4

%.MisconceptionsMainarticle:AnumberofmisconceptionshavearisensurroundingHIV/AIDS.ThreeofthemostcommonarethatAIDScanspreadthroughcasualcontact,thatsexualintercoursewithavirginwillcureAIDS,andthatHIVcaninfectonlyhomosexualmenanddrugusers.OthermisconceptionsarethatanyactofanalintercoursebetweengaymencanleadtoAIDSinfection,andthatopendiscussionofhomosexualityandHIVinschoolswillleadtoincreasedratesofhomosexualityandAIDS.PathophysiologyThissectionmayrequiretomeetWikipedia's.Pleaseifyoucan.(April2023)ThepathophysiologyofAIDSiscomplex,asisthecasewithall.Ultimately,HIVcausesAIDSbydepletingCD4+Thelperlymphocytes.Thisweakenstheimmunesystemandallows.Tlymphocytesareessentialtotheimmuneresponseandwithoutthem,thebodycannotfightinfectionsorkillcancerouscells.ThemechanismofCD4+Tcelldepletiondiffersintheacuteandchronicphases.Duringtheacutephase,HIV-inducedcelllysisandkillingofinfectedcellsbyaccountsforCD4+Tcelldepletion,althoughmayalsobeafactor.Duringthechronicphase,theconsequencesofgeneralizedimmuneactivationcoupledwiththegraduallossoftheabilityoftheimmunesystemtogeneratenewTcellsappeartoaccountfortheslowdeclineinCD4+Tcellnumbers.AlthoughthesymptomsofimmunedeficiencycharacteristicofAIDSdonotappearforyearsafterapersonisinfected,thebulkofCD4+Tcelllossoccursduringthefirstweeksofinfection,especiallyintheintestinalmucosa,whichharborsthemajorityofthelymphocytesfoundinthebody.ThereasonforthepreferentiallossofmucosalCD4+TcellsisthatamajorityofmucosalCD4+TcellsexpresstheCCR5coreceptor,whereasasmallfractionofCD4+Tcellsinthebloodstreamdoso.HIVseeksoutanddestroysCCR5expressingCD4+cellsduringacuteinfection.Avigorousimmuneresponseeventuallycontrolstheinfectionandinitiatestheclinicallylatentphase.However,CD4+Tcellsinmucosaltissuesremaindepletedthroughouttheinfection,althoughenoughremaintoinitiallywardofflife-threateninginfections.ContinuousHIVreplicationresultsinastateofgeneralizedimmuneactivationpersistingthroughoutthechronicphase.Immuneactivation,whichisreflectedbytheincreasedactivationstateofimmunecellsandreleaseofproinflammatory,resultsfromtheactivityofseveralHIVgeneproductsandtheimmuneresponsetoongoingHIVreplication.AnothercauseisthebreakdownoftheimmunesurveillancesystemofthemucosalbarriercausedbythedepletionofmucosalCD4+Tcellsduringtheacutephaseofdisease.Thisresultsinthesystemicexposureoftheimmunesystemtomicrobialcomponentsofthegut’snormalflora,whichinahealthypersoniskeptincheckbythemucosalimmunesystem.TheactivationandproliferationofTcellsthatresultsfromimmuneactivationprovidesfreshtargetsforHIVinfection.However,directkillingbyHIValonecannotaccountfortheobserveddepletionofCD4+TcellssinceonlyofCD4+Tcellsinthebloodareinfected.AmajorcauseofCD4+Tcelllossappearstoresultfromtheirheightenedsusceptibilitytoapoptosiswhentheimmunesystemremainsactivated.AlthoughnewTcellsarecontinuouslyproducedbythetoreplacetheoneslost,theregenerativecapacityofthethymusisslowlydestroyedbydirectinfectionofitsbyHIV.Eventually,theminimalnumberofCD4+Tcellsnecessarytomaintainasufficientimmuneresponseislost,leadingtoAIDSCellsaffectedThe,enteringthroughwhicheverroute,actsprimarilyonthefollowingcells::CD4+Certaincells:ofthenervoussystem-indirectlybytheactionofandtheTheeffectThehasbuthowitdoesitisstillnotquiteclear.Itcanremaininactiveinthesecellsforlongperiods,though.ThiseffectishypothesizedtobeduetotheCD4-gp120interaction.ThemostprominenteffectoftheHIVvirusisitsT-helpercellsuppressionandlysis.Thecellissimplykilledofforderangedtothepointofbeingfunction-less(theydonotrespondtoforeign).TheinfectedB-cellscannotproduceenoughantibodieseither.ThustheimmunesystemcollapsesleadingtothefamiliarAIDScomplications,likeinfectionsandneoplasms(videsupra).InfectionofthecellsoftheCNScauseacute,subacute,vacuolarmyelopathyand.Lateritleadstoevencomplex.TheCD4-gp120interaction(seeabove)isalsopermissivetootherviruseslike,,virus,etc.Thesevirusesleadtofurthercelldamage.cytopathy.MolecularbasisFordetails,see:DiagnosisThediagnosisofAIDSinapersoninfectedwithHIVisbasedonthepresenceofcertainsignsorsymptoms.SinceJune5,1981,manydefinitionshavebeendevelopedforsurveillancesuchastheandthe.However,clinicalstagingofpatientswasnotanintendeduseforthesesystemsastheyareneithersensitive,norspecific.Indevelopingcountries,thestagingsystemforHIVinfectionanddisease,usingclinicalandlaboratorydata,isusedandindevelopedcountries,the(CDC)ClassificationSystemisused.WHOdiseasestagingsystemMainarticle:In1990,the(WHO)groupedtheseinfectionsandconditionstogetherbyintroducingastagingsystemforpatientsinfectedwithHIV-1.AnupdatetookplaceinSeptember2023.Mostoftheseconditionsarethatareeasilytreatableinhealthypeople.StageI:HIVinfectionisandnotcategorizedasAIDSStageII:includesminormanifestationsandrecurrentinfectionsStageIII:includesunexplainedforlongerthanamonth,severebacterialinfectionsandtuberculosisStageIV:includesofthe,ofthe,,orand;thesediseasesareindicatorsofAIDS.CDCclassificationsystemMainarticle:TherearetwomaindefinitionsforAIDS,bothproducedbythe(CDC).TheolderdefinitionistoreferringtoAIDSusingthediseasesthatwereassociatedwithit,forexample,,thediseaseafterwhichthediscoverersofHIVoriginallynamedthevirus.In1993,theCDCexpandedtheirdefinitionofAIDStoincludeallHIVpositivepeoplewithaCD4+Tcellcountbelow200perµLofbloodor14%ofall.ThemajorityofnewAIDScasesinuseeitherthisdefinitionorthepre-1993CDCdefinition.TheAIDSdiagnosisstillstandsevenif,aftertreatment,theCD4+Tcellcountrisestoabove200perµLofbloodorotherAIDS-definingillnessesarecured.HIVtestMainarticle:ManypeopleareunawarethattheyareinfectedwithHIV.Lessthan1%ofthesexuallyactiveurbanpopulationinAfricahasbeentested,andthisproportionisevenlowerinruralpopulations.Furthermore,only%ofpregnantwomenattendingurbanhealthfacilitiesarecounseled,testedorreceivetheirtestresults.Again,thisproportionisevenlowerinruralhealthfacilities.Therefore,andbloodproductsusedinmedicineandmedicalresearcharescreenedforHIV.HIVtestsareusuallyperformedonvenousblood.Manylaboratoriesusefourthgenerationscreeningtestswhichdetectanti-HIVantibody(IgGandIgM)andtheHIVp24antigen.ThedetectionofHIVantibodyorantigeninapatientpreviouslyknowntobenegativeisevidenceofHIVinfection.IndividualswhosefirstspecimenindicatesevidenceofHIVinfectionwillhavearepeattestonasecondbloodsampletoconfirmtheresults.The(thetimebetweeninitialinfectionandthedevelopmentofdetectableantibodiesagainsttheinfection)canvarysinceitcantake3–6

monthstoandtotestpositive.Detectionofthevirususingpolymerasechainreaction()duringthewindowperiodispossible,andevidencesuggeststhataninfectionmayoftenbedetectedearlierthanwhenusingafourthgenerationEIAscreeningtest.PositiveresultsobtainedbyPCRareconfirmedbyantibodytests.RoutinelyusedHIVtestsforinfectionin,borntoHIV-positivemothers,havenovaluebecauseofthepresenceofmaternalantibodytoHIVinthechild'sblood.HIVinfectioncanonlybediagnosedbyPCR,testingforHIVpro-viralDNAinthechildren's.PreventionEstimatedperactriskforacquisition

ofHIVbyexposurerouteExposureRouteEstimatedinfections

per10,000exposures

toaninfectedsourceBloodTransfusion9,000Childbirth2,500Needle-sharinginjectiondruguse67Percutaneousneedlestick30Receptiveanalintercourse*50Insertiveanalintercourse*Receptivepenile-vaginalintercourse*10Insertivepenile-vaginalintercourse*5Receptiveoralintercourse*§1Insertiveoralintercourse*§*assumingnocondomuse

§sourcereferstooralintercourse

performedonamanThethreemaintransmissionroutesofHIVare,exposuretoinfectedbodyfluidsortissues,andfrommothertoorchildduringperiod.ItispossibletofindHIVinthe,,andofinfectedindividuals,buttherearenorecordedcasesofinfectionbythesesecretions,andtheriskofinfectionisnegligible.SexualcontactThemajorityofHIVinfectionsareacquiredthroughrelationsbetweenpartners,oneofwhomhasHIV.TheprimarymodeofHIVinfectionworldwideisthroughsexualcontactbetweenmembersoftheoppositesex.Duringasexualact,onlymaleorfemalecanreducethechancesofinfectionwithHIVandotherSTDsandthechancesofbecoming.ThebestevidencetodateindicatesthattypicalcondomusereducestheriskofHIVtransmissionbyapproximately80%overthelong-term,thoughthebenefitislikelytobehigherifcondomsareusedcorrectlyoneveryoccasion.Themalecondom,ifusedcorrectlywithoutoil-basedlubricants,isthesinglemosteffectiveavailabletechnologytoreducethesexualtransmissionofHIVandothersexuallytransmittedinfections.Manufacturersrecommendthatoil-basedlubricantssuchas,butter,andnotbeusedwithlatexcondoms,becausetheydissolvethe,makingthecondoms.Ifnecessary,manufacturersrecommendusing-basedlubricants.Oil-basedlubricantscanhoweverbeusedwithcondoms.Theisanalternativetothemalecondomandismadefrom,whichallowsittobeusedinthepresenceofoil-basedlubricants.Theyarelargerthanmalecondomsandhaveastiffenedring-shapedopening,andaredesignedtobeinsertedintothevagina.Thefemalecondomcontainsaninnerring,whichkeepsthecondominplaceinsidethevagina

–insertingthefemalecondomrequiressqueezingthisring.However,atpresentavailabilityoffemalecondomsisverylowandthepriceremainsprohibitiveformanywomen.Preliminarystudiessuggestthat,wherefemalecondomsareavailable,overallprotectedsexualactsincreaserelativetounprotectedsexualacts,makingthemanimportantHIVpreventionstrategy.Studiesoncoupleswhereonepartnerisinfectedshowthatwithconsistentcondomuse,HIVinfectionratesfortheuninfectedpartnerarebelow1%peryear.Preventionstrategiesarewell-knownindevelopedcountries,butepidemiologicalandbehavioralstudiesinEuropeandNorthAmericasuggestthatasubstantialminorityofyoungpeoplecontinuetoengageinhigh-riskpracticesdespiteHIV/AIDSknowledge,underestimatingtheirownriskofbecominginfectedwithHIV.haveshownthatmalelowerstheriskofHIVinfectionamongheterosexualmenbyupto60%.ItisexpectedthatthisprocedurewillbeactivelypromotedinmanyofthecountriesaffectedbyHIV,althoughdoingsowillinvolveconfrontinganumberofpractical,culturalandattitudinalissues.Someexpertsfearthatalowerperceptionofvulnerabilityamongcircumcisedmenmayresultinmoresexualrisk-takingbehavior,thusnegatingitspreventiveeffects.However,onerandomizedcontrolledtrialindicatedthatadultmalecircumcisionwasnota