http://www.imdb.com/title/tt0816711/
Rule number one on writing zombie lore. Never paint yourself into a corner by giving away too many hard details.
Unless there is a good shock value in so doing, and the ‘rules’ were based upon what the characters thought the rules were.
In “The Walking Dead” the ‘rule’ seemed to be that only those bitten by a zombie became a ‘walker’ when they died. Now it seems that anyone exposed (and it seems they all got exposed through their rather casual handling of beheaded walkers) who dies rises as a ‘walker’. YIKES!!!