essence drain, contagion and intense agony

Hey, quick mechanics question. If i put intense agony into Essence Drain, cast it on a mob and then put contagion on it and it dies:

a) does the new ED debuff has the buff of intense agony, despite that the mob probably already has less then full life?

or b) is the new instance of ED calculated completely new?

it's definetly not hitting again, cause it can't suddenly proc ailments, so if it just transfers the initial debuff and calculates stuff like withered, that would be fine. if not, intense agony would be just the most stupid support gem.