这里的to have been affected 是不定式的完成时态做后置定语,修饰前面的people.但这样用法比较少见,通常用一个定语从句来代替,people who have been affected.
英语中某些名词,如chance,way,ability,time,right（权利）等后面是可以用不定式做其后置定语的.如：I got a chance to study abroad.这里的to study abroad 做定语,修饰chance；the way to learn English 这里的to learn English 也是修饰way的.