The incredible fantastic world of pretend make believe reality...
Zombies don't know that if they bite you you turn into a zombie. Because, they are unaware. They function on a basic instinct of feeding. They don't know anything because all they know is to be a zombie. Some of them have been zombies all their death (life). All you must do is survive and look for others who are not zombies. Remember a zombie does not know it is a zombie. Just like the dead don't know they are dead and the stupid don't know they are stupid.