I love "pink-eye" campaigns where everything can potentially kill you. 0-level commoner can easily kill their 20th level king by accidentally serving him the wrong mushrooms in the stew.
Those undercooked pork tacos your 5th level wizard bought from the street vendor? Surely they're safe to eat...
That slash across the thigh your 10th level warrior got during the fight with the goblins? Just a flesh wound turns into gas gangrene if you're not so lucky. Even if you're lucky, plan on bed rest for the next week if you have any hope of keeping the leg.