▁newer ▁European ▁imm igr ants ▁assumed ▁that ▁there ▁had ▁always ▁been ▁relatively ▁few ▁ind igen ous ▁pe op les . ▁The ▁scope ▁of ▁the ▁ep ide m ics ▁over ▁the ▁years ▁was ▁trem end ous , ▁killing ▁millions ▁of ▁people — poss ibly ▁in ▁excess ▁of ▁ 9 0 % ▁of ▁the ▁population ▁in ▁the ▁hard est - hit ▁areas — and ▁creating ▁one ▁of ▁" the ▁greatest ▁human ▁cat ast rop he ▁in ▁history , ▁far ▁exceed ing ▁even ▁the ▁dis aster ▁of ▁the ▁Black ▁Death ▁of ▁medieval ▁Europe ", ▁which ▁had ▁killed ▁up ▁to ▁one - third ▁of ▁the ▁people ▁in ▁Europe ▁and ▁Asia ▁between ▁ 1 3 4 7 ▁and ▁ 1 3 5 1 . ▁ ▁One ▁of ▁the ▁most ▁dev ast ating ▁dise ases ▁was ▁small po x , ▁but ▁other ▁dead ly ▁dise ases ▁included ▁ty ph us , ▁meas les , ▁influen za , ▁b ub onic ▁pl ague , ▁ch ol era , ▁mal aria , ▁t uber cul osis , ▁m umps , ▁yellow ▁fe ver ▁and ▁pert uss is , ▁which ▁were ▁chron ic ▁in ▁E uras ia . ▁ ▁This ▁transfer ▁of ▁disease ▁between ▁the ▁Old ▁and ▁New ▁World s ▁was ▁later ▁studied ▁as ▁part ▁of ▁what ▁has ▁been ▁l abeled ▁the ▁" Col umb ian ▁Exchange ". ▁ ▁The ▁ep ide m ics ▁had ▁very ▁different ▁effects ▁in ▁different ▁regions ▁of ▁the ▁Amer icas . ▁The ▁most ▁vulner able ▁groups ▁were ▁those ▁with ▁a ▁relatively ▁small ▁population ▁and ▁few ▁built -