LitCharts assigns a color and icon to each theme in The 5th Wave, which you can use to track the themes throughout the work.
Trust and Belief
Survival and Perseverance
Warfare and Dehumanization
Family
Summary
Analysis
Zombie feels numb as he finally recovers his senses after the Wonderland procedure. Dr. Pam explains that she had to look inside him because the aliens infect people from the inside. These infected people embedded themselves in the miliary, and now about one out of every three humans on Earth is infected.
Pam’s comment that about a third of the people on earth are “infected” reflects again how people in this apocalypse can’t trust their eyes and can’t rely on one another. The comparison of this distrust to an “infection” shows how distrust is contagious and how one person acting suspicious can cause others to do the same to protect themselves.