Zone 4 is impossible. You can only have 5 people sick, but you start with 5 sick, and they will not isolate at all... Out of 5 people who have the illness, 4 say they will not isolate. That's 80%, not 40. The chances of having 4/5 when the chance is 40% of not isolating is actually pretty low, yet that seems to happen a LOT. I don't think that this game is doable in any reasonable respect. The percentages are definitely not in line with what's going on in the game.