If you are infected but have a fire extinguisher, you can set your infected members on fire to burn off the infection. And then just simply use the extinguisher to put them out, infection free :D
I LOVE THIS GAME! the one thing i would change is add a "negotiate button" where you could call out to the other humans and 1/5 of them would join you BUT some would say yes and then when they got close shoot you! so youd have to be careful!