The “zombies” in this lore are not undead—by all appearances, they appear to be living, breathing people. It’s well known by this point though that those infected by the outbreak seem to enter into a mindless state, and endlessly search for their next meal of uninfected flesh.
Exposure to blood or saliva from an infected individual in exposed areas of the skin seems to lead to a near inevitable infection, and consequently the mindless state that most infected linger.
The city of Chicago has been firebombed extensively. Survivors actually living in this area is highly unlikely.
Established near the start of the outbreak, nearly the entire state of Illinois had a blockade constructed to contain the infection. As of the end of chapter one, The Road Ahead, this line has since been breached, and the infection has broken out into the rest of the nation.
Despite their initial attempts, FEMA doesn’t seem to have a presence any longer within the original Illinois quarantine area.
The CEITA organization, the group fighting for the infected to be viewed as ill individuals and not mindless threats, seems to have broken up entirely. The leadership reportedly vanished under mysterious circumstances, and any lower-level members have largely been left on their own.