Here's something I thought of while working on "Red Markets: Black Death" (working title) that might make an interesting change to infection rolls: Have the
victim's player roll the Black die, and the Market roll the Red die. The player will have a semi-informed guess about how likely they are to have been infected, but no certain knowledge either way. Seems to me that this could simulate the details of the infectious incident, and reflect the fact that the victim would likely have some sense of how badly they had been got (Black 1: bad bite near a major blood vessel; Black 9: got some spit on me, but nothing seems to have broken the skin). It could really play up the unique horror of the situation, and lead to some cool roleplaying as the victim tries to convince their allies one way or the other. For extra pizzazz, maybe the victim's player isn't allowed to tell the other players the number that they rolled, only a description of their injuries.
Anyway, that's pretty hardcore co-designer-style feedback, so take it or leave it, Caleb.