What is the theme in A Summer to Die by Lois Lowry?

The main underlying theme that emerges in A Summer to Die by Lois Lowry is the unending cycle of life. No matter what the losses that are experienced, life continues in its own mysterious and varied ways. The thirteen-year-old Meg Chalmers must deal with the sickness of her fifteen-year-old sister, Molly, and ultimately her untimely passing. In the scheme of things, no one could argue that it's fair for a young person just beginning her life to die. But Charles Chalmers, Meg's father, tells Meg that disease is something that happens and that man has no control over who is struck with it. Disease is part of life.