, ▁which ▁is ▁a ▁mixture ▁of ▁yellow ▁and ▁black ▁flags ▁previously ▁used . ▁It ▁is ▁sometimes ▁called ▁the ▁" yellow ▁jack " ▁but ▁this ▁was ▁also ▁a ▁name ▁for ▁yellow ▁fe ver , ▁which ▁probably ▁der ives ▁its ▁common ▁name ▁from ▁the ▁flag , ▁not ▁the ▁colour ▁of ▁the ▁vict ims ▁( ch ol era ▁ships ▁also ▁used ▁a ▁yellow ▁flag ). ▁The ▁plain ▁yellow ▁flag ▁(" Que bec " ▁or ▁Q ▁in ▁international ▁mar itime ▁signal ▁flags ) ▁probably ▁der ives ▁its ▁letter ▁symbol ▁for ▁its ▁initial ▁use ▁in ▁quar antine , ▁but ▁this ▁flag ▁in ▁modern ▁times ▁indicates ▁the ▁opposite — a ▁ship ▁that ▁' requests ▁free ▁pr atique ', ▁i . e . ▁that ▁decl ares ▁itself ▁free ▁of ▁quar antin able ▁disease , ▁and ▁requests ▁board ing ▁and ▁routine ▁port ▁ins pection . ▁ ▁Eth ical ▁and ▁practical ▁consider ations ▁The ▁quar ant ining ▁of ▁people ▁often ▁ra ises ▁questions ▁of ▁civil ▁rights , ▁especially ▁in ▁cases ▁of ▁long ▁conf in ement ▁or ▁seg reg ation ▁from ▁society , ▁such ▁as ▁that ▁of ▁Mary ▁Mall on ▁( also ▁known ▁as ▁Ty ph oid ▁Mary ), ▁a ▁ty ph oid ▁fe ver ▁car rier ▁who ▁was ▁arrested ▁and ▁quar ant ined ▁in ▁ 1 9 0 7 ▁and ▁later ▁spent ▁the ▁last ▁ 2 3 ▁years ▁and ▁ 7 ▁months ▁of ▁her ▁life ▁in ▁medical ▁isol ation ▁at ▁R ivers ide ▁Hospital ▁on ▁North ▁Bro ther ▁Island . ▁ ▁The ▁United ▁Nations ▁and ▁the ▁Si rac usa ▁Princi ples ▁Gu