Hey I really like this! One bit of criticism: It'd be nice to have a visual indicator of who is infected and who isn't. Maybe its already there but I had a hard time telling and resorted to just watching who came into contact with the rats and who didn't. I also think a more obvious/game-affecting effect when you heal someone would be nice.
Overall though, once I figured that out I had a fun time trying to see how long I could last. Gets really frantic when you get down to that last couple percent.
Nice job!