HIVisablood-bomevirustransmittedviasexualintercourseorpercutaneousexposuretoinfectedblood,orfromaninfectedmothertoherchildduringthebirthprocess.Followinginfection,thetimebeforeonsetofclinicaldiseasevariesfrommonthstoyears;thedurationisinfluencedbyage(therateofprogressionincreaseswithage)andHLAtype(A1,B8,DR3areassociatedwithrapidprogressionandB27withslowprogression),butnotbygenderorriskactivity.Althoughmostpatientsinitiallyhavenocharacteristicsymptoms,thereisusually(90%)agradualdeclineinimmunefunction.
