highly unlikely assuming the underwear was clean (who would wear someone's dirty underwear? ). i have never heard of a case were hiv was transmitted via clothing. wear your own underwear or go commando.
am i at risk of getting "hiv"? . i don't wear underwear but today i wore underwear of a person who has "aids" but he has not wore his underwear since 1 month but today i wore it i have no sore or wounds on my penis am i at risk?