What does being “sick” mean?
If your team comes gets into contact with zombies (either the zombie horde chasing you from behind or a pocket of zombies ahead of you), your character will take damage. How much damage you take is determined by the zombies’ FEROCITY. Beware, as the challenge progresses, the zombies get more ferocious and do more damage, more quickly.
If your health is reduced to zero, you will enter the SICK state and have 24 hours to recover some health (by spending Power to heal yourself). If you do not heal yourself before the SICK state runs out, you will turn into a zombie.
If you are turned into a zombie, you may choose to spend your steps to further the progress of the zombie horde, or you may spend your steps and/or Power to regain health. If you regain full health, you will rejoin your former human team.