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inthe20yearssincethefirstcasesofaidsweredetected,scientistssaytheyhavelearnedmoreaboutthisviraldiseasethananyother.
yetpeterpiot,whodirectstheunitednationsaidsprogram,andstefanovellaofrome,presidentoftheinternationalaidssociety,andotherexpertssayreviewingunansweredquestionscouldproveusefulasameasureofprogressforaidsandotherdiseases.
amongtheimportantbroaderscientificquestionsthatremain：
whydoesaidspredisposeinfectedpersonstocertaintypesofcancerandinfections？
along-standingbeliefisthatcancercellsconstantlydevelopandareheldincheckbyahealthyimmunesystem.butaidshaschallengedthatbelief.peoplewithaidsaremuchmorepronetocertaincancerslikenon-hodgkinslymphomasandkaposi’ssarcoma,butnottobreast,colonandlung,themostcommoncancersintheunitedstates.thispatternsuggeststhatanimpairedimmunesystem,atleastthetypethatoccursinaids,doesnotallowcommoncancerstodevelop.
whatroutedoeshivtakeafteritentersthebodytodestroytheimmunesystem？
whenhivistransmittedsexually,thevirusmustcrossatissuebarriertoenterthebody.howthathappensisstillunclear.thevirusmightinvadedirectlyorbecarriedbyaseriesofdifferentkindsofcells.
eventuallyhivtravelsthroughlymphvesselstolymphnodesandtherestofthelymphsystem.butwhatisnotknownishowthevirusproceedstodestroythebody’scd-4cellsthatareneededtocombatinvadinginfectiousagents.
howdoeshivsubverttheimmunesys-tem？
althoughhivkillstheimmunecellssenttokillthevirus,thereiswidespreadvariationintherateatwhichhivinfectedpeoplebecomeillwithaids.soscientistsask：cantheelementsoftheimmunesystemresponsibleforthatvariabilitybeidentified？ifso,cantheybeusedtostopprogressiontoaidsininfectedindividualsandpossiblypreventinfectioninthefirstplace？
whatisthemosteffectiveanti-hivtherapy？
intheory,earlytreatmentshouldofferthebestchanceofpreservingimmunefunction.butthenewdrugsdonotcompletelyeliminatehivfromthebodysothemedicines,whichcanhavedangeroussideeffects,willhavetobetakenforalifetimeandperhapschangedtocombatresistance.thenewpolicyisexpectedtorecommendthattreatmentbedeferreduntiltherearesignstheimmunesystemisweakening.
isavaccinepossible？
thereislittlequestionthataneffectivevaccineiscrucialtocontrollingtheepidemic.yetonlyonehasreachedthestageoffulltesting,andthereiswidecontroversyoverthedegreeofprotectionitwillprovide.hivstrainsthataretransmittedinvariousareasoftheworlddiffergenetically.itisnotknownwhetheravaccinederivedfromonetypeofhivwillconferprotectionagainstothertypes.
intheabsenceofavaccine,howcanhivbestopped？
withoutmoreincisive,focusedbehavioralresearch,preventionmessagesalonewillnotstoptheglobalepidemic.