Getting bit by Trioxin zombie in the previous two Return of the Living Dead films did not turn the individual bit into a zombie. However in Return of the Living Dead III it does.
Director Brian Yuzna on the DVD commentary regrets not coming up with a more proper name for the film as "Return of the Living Dead III" is too long. He suggests the title "Kurt and Julie" and admits that the title "Mortal Zombie" (which it was called in some places in Europe) is a nice name.