I suspect you misunderstood the metaphor. If original sin were transmitted like Hepatitis (or any known blood-borne disease), it would be simple enough to avoid. Simply don't consume or touch blood and you won't get it.
They, obviously, don't refer to physical blood. Rather, it is the same type referred to in the saying "blood is thicker than water." This refers to familial relation. Since we are descended from Adam, we are all of "Adam's blood."
Sometimes, blood is also invoked as the instrument of our salvation, as in the reading from
Revelation last Sunday.
I would posit the most dangerous aspect of such a line of thinking is that it could lead one perilously close to St Anselm's
refuted satisfaction theory. Indeed, many evangelical Protestants have bought it, hook, line and sinker.