Chad Urso McDaniel
Game mechanically it makes sense (to avoid an outbreak), but thematically it feels a bit weird to supply a city that already has a plague cube on it. So to be sure I ask the question: can you supply a city that already has a plague cube?
Yes, and thematically I think of it as the Plague cubes indicate how bad it is in that city going from 1-3. These are steps towards a critical infection level. We still have the ability to stabilize the city, but it's looking bad.
Our job, even if a city has one cube, is to deliver supplies so that the infection doesn't hit critical mass.