BasicFactsAboutHIV/AIDSWhatisHIV?HIVisthehumanimmunodeficiencyvirusthatcausesAIDS.Amemberofagroupofvirusescalledretroviruses,HIVinfectshumancellsandusestheenergyandnutrientsprovidedbythosecellstogrowandreproduce.WhatisAIDS?AIDS(acquiredimmunodeficiencysyndrome)isadiseaseinwhichthebody'simmunesystembreaksdownandisunabletofightoffcertaininfections,knownas"opportunisticinfections,"andotherillnessesthattakeadvantageofaweakenedimmunesystem.WhenapersonisinfectedwithHIV,thevirusentersthebodyandlivesandmultipliesprimarilyinthewhitebloodcells.Thesearetheimmunecellsthatnormallyprotectusfromdisease.ThehallmarkofHIVinfectionistheprogressivelossofaspecifictypeofimmunecellcalledT-helperorCD4cells.Asthevirusgrows,itdamagesorkillstheseandothercells,weakeningtheimmunesystemandleavingtheindividualvulnerabletovariousopportunisticinfectionsandotherillnesses,rangingfrompneumoniatocancer.TheU.S.CentersforDiseaseControlandPrevention(CDC)definessomeoneashavingaclinicaldiagnosisofAIDSiftheyhavetestedpositiveforHIVandmeetoneorbothoftheseconditions:•TheyhaveexperiencedoneormoreAIDS-relatedinfectionsorillnesses;•ThenumberofCD4cellshasreachedorfallenbelow200percubicmillimeterofblood(ameasurementknownasT-cellcount).Inhealthyindividuals,theCD4countnormallyrangesfrom450to1200.HowquicklydopeopleinfectedwithHIVdevelopAIDS?Insomepeople,theT-celldeclineandopportunisticinfectionsthatsignalAIDSdevelopsoonafterinfectionwithHIV.Mostpeopleremainasymptomaticfor10to12years,andafewformuchlonger.用心爱心专心Aswithmostdiseases,earlymedicalcarecanhelpprolongaperson'slife.HowmanypeopleareaffectedbyHIV/AIDS?TheJointUnitedNationsProgrammeonHIV/AIDS(UNAIDS)estimatesthattherearenowover40millionpeoplelivingwithHIVorAIDSworldwide.MostofthemdonotknowtheycarryHIVandmaybespreadingthevirustoothers.HereintheU.S.,nearlyonemillionpeoplehaveHIVinfectionorAIDS,orroughlyoneoutofevery250people.Atleast40,000AmericansbecomenewlyinfectedwithHIVeachyear,anditisestimatedthathalfofallpeoplewithHIVintheU.S.havenotbeentestedanddonotknowtheyarecarryingthevirus.Sincethebeginningoftheepidemic,AIDShaskilledmorethan30millionpeopleworldwide,includingmorethan500,000Americans.AIDShasreplacedmalariaandtuberculosisastheworld'sdeadliestinfectiousdiseaseamongadultsandisthefourthleadingcauseofdeathworldwide.Over13millionchildrenhavebeenorphanedbytheepidemic.HowisHIVtransmitted?ApersonwhoisHIV-infectedcarriesthevirusincertainbodyfluids,includingblood,semen,vaginalsecretions,andbreastmilk.TheviruscanbetransmittedonlyifsuchHIV-infectedfluidsenterthebloodstreamofanotherperson.Thiskindofdirectentrycanoccur(1)throughtheliningsofthevagina,rectum,mouth,andtheopeningatthetipofthepenis;(2)throughintravenousinjectionwithasyringe;or(3)throughabreakintheskin,suchasacutorsore.Usually,HIVistransmittedthrough:•Unprotectedsexualintercourse(eithervaginaloranal)withsomeonewhoisHIVinfected.WomenareatgreaterriskofHIVinfectionthroughvaginalsexthanmen,althoughtheviruscanalsobetransmittedfromwomentomen.Analsex(whethermale-maleormale-female)posesahighriskmainlytothereceptivepartner,becausetheliningoftheanusandrectumareextremelythinandfilledwithsmallbloodvesselsthatcanbeeasilyinjuredduringintercourse.•UnprotectedoralsexwithsomeonewhoisHIVinfected.用心爱心专心TherearefarfewercasesofHIVtransmissionattributedtooralsexthantoeithervaginaloranalintercourse,butoral-genitalcontactpos...
