Bacterial

In the city of Tenchi, people live average lives, with average people, with no problems whatsoever. That is, however, untill one faithful day when one person messed up, screwing up the city, killing millions. What is left of Tenchi is insanity. People killing other people, many screams, and no sign of civilized people at all. The only people "Alive" are people under the age of 13, children. What will they do? How will they survive? Read to find out.