There has been a epidemic (sickness spread rapidly) only 18 and under survive all 19 and older die. This does not mean if you turn 18 your for sure going to die it's just the kids in those generations were born with something no adult had formed. Now about the plaque it mutates every couple months but no child dies from it. There is a group of 7 children 12-17 they Were in school when the sickness became air born to all adults. Read to find out what happens DISCLAIMER THIS IS INTACT MY FIRST BOOK DO NOT JUDGE ME IN ANYWAY THAT IS BAD. Please and thank you have a nice day