This refers to the level by which a sickness must have mutated to increase in potency that a sickness that was formerly diagnosed as man-flu has when it is passed on to the heartless s.o.b. that misdiagnosed the sickness to begin with...of course this is due to the fact the the sickness MUST HAVE gotten more powerful upon contagion because the diagnoser claims to not be exagerating the misery but will not apologize for claiming that the diagnosee had.
This in one of the most readily documented instances of instant Karma
Her - Honey, this flu miserable. I want to die. I didn't realize it was that bad when you first had it. It must have gotten stronger since you gave it to me.
Him - That's right. Who's the baby now? I guess you weren't aware of this bug's contaigery.