The problem with zombies is they apparently lack the awareness of injury leading to infection and further damage. Most televised zombies appear to be in the multiple injury state and so one would ask if zombies, once re-animated go though an initial period of
Agoraphobia, preferring to stay alone for a period of time, injuring themselves without knowing and at a later stage acting on a herding instinct outside in a state of infected decay.
Its a theory open to conjecture. In the documentary '
Dawn of the Dead' and its follow up documentary '
Shawn of the Dead' show the zombies in an advanced state of injury at an accelerated level.