The snow has been piling up tremendously. Christmas was also coming up. Also, snow has been piling up so much, that he protagonists family takes on skiing. A few days later, everyone but Miranda gets the flu. She is left responsible for caring for them.
A theme that I am currently getting from the book is that you should love, and cherish your family. I say this because when anything is hard, they have each others backs. Like when Miranda helped her family while they were sick. She did that because she loves her family. Without each other, none of them would be alive. Them sticking together is helping them survive the inevitable.
Surviving in this world is now almost impossible. everyone is becoming sick, and most are dying. They all must make the best decisions to survive longer. Even if it means giving up eating lunch. For example. They are now almost out of food. Miranda and her mother are now giving up eating often so her brothers can survive longer.
We have seen this family change massively since the beginning of this story. Their entire family is becoming selfless for each other.