Love the idea and amazing execution! The game is really polished under every aspect, impressive work!
The only thing gameplay wise is that you can just keep clumping infected people together by drawing circles on the same spots and do the same with non-infected ones and it becomes really easy to win (except the last level hehe) and their different character paths don't really matter anymore.
Maybe if you could only draw straight lines so the pathing mechanic is used more! Not sure about that. Anyways, great game guys!