Here's the question though, since we know mafia had the antibody, do they also have the venom?
It's kind of like making a problem and selling the solution, it's quite within the possibilities; and probably why we haven't heard from the one who has poisoned me.
If they had come forward earlier it is possible that they could've been given the benefit of doubt for being Town, but now they will probably have to take their secret to their grave.