Whatever It Takes
Paul and Will are men that will protect their families no matter what they have to do to ensure their safety. We see also that Sarah and Kim are of the same cloth. In a world where it appears no one can be trusted, these families are on edge with one another in both subtle and obvious ways as their main goal is to protect their family.
Paranoia
This theme is present throughout the film as we have no understanding as to how this contagion came about, nor how people contract it or where it came from. Thus, because of the lack of sufficient evidence, everyone is paranoid as they could contract this unknown disease in any number of ways. With the world having gone mad and no communication to major cities, the identities of everyone remains murky as well. This causes the film to have a feeling of paranoia, that something insidious is lurking.
Outbreak
The reason that the events of this story happen is because of a deadly outbreak that has apparently wiped out cities in America. People are running from the heavily populated areas in order to find safety and shelter; Will and his family represent these people running for their lives. And Paul's family represent those people who were not exposed to the epicenter of the outbreak but are experiencing its effects. Moreover, they are people who want to defend themselves from further infection from those exposed at the core of the breakout in the city.
