[Dean only cares about the reflection in so much as it's a clue to what he really is, or what kind of vampire he is. That's the part he's always hated: supernatural creatures are so picky. They have to be identified exactly right, killed exactly right, or there's just a world of hurt waiting on the other side of a botched hunt.

He tips his head to acknowledge the bit about mirrors and silver - it's an idea, one of the ones with a question mark after it instead of a line through it on his mental list - but doesn't get distracted. From that, anyway: he picks up the shake without seeming to notice he's done it. Having something else to focus on besides how shitty he feels, both physically and mentally, is enough for the time being, though he gives the shake a dubious look after he takes a drink of it and puts it down again, his gut twisting in otherwise unacknowledged protest.]

We need to find out why he's biting. If he's that weak or if he's doing something else.

If the bite does something else, like gives him access for possession or influence. That's as important as finding out how to put him down.

[It's not, Dean would say if he knew. It's not different at all.]