I have a base system for a zombie one shot that uses the Cortex rule system. It falls under that survival aspect that you are talking about. I have a 50% chance of infection (that the player DOES NOT KNOW if it takes). It causes some fun times, as the player thinks he is okay, and sometimes he isn't but the group will shun/suspect him. I was considering making a small 2-3 hour map on roll 20. I should work on it...