What is the main conflict in The Dead and the Gone by Susan Beth Pfeffer?

"The Dead and the Gone" is a dark and frightening tale about the Earth following a catastrophe that leaves the world torn and society fragmented. It is a story of faith, hope, desperation, and sacrifice that follows one family, the Morales, through their trials and tribulations. They are led through the chaos by Alex Morales, a seventeen-year-old young man who discovers through the novel that he is stronger than he realized, and that his faith, along with his family, can survive.