So, we were just playing a game (on Steam) against Plague Rat in the Pike Industrial Complex, and it turned into the slowest Plague Rat game I've ever seen.
The Environment got two Checmical Explosions, and then two Biomemetic Plasma Vats, two Supercooled Trisolven Vats, and three rats before getting an Irridated Cyclohexane Vat.
Which meant that all non-irreducible damage was at -2, everyone healed 2 hp a turn, and very little damage was dealt. And the only infected hero was Mr. Fixer, who had Mantis out. So the game took a while.