When you are bitten by a zombie, you have to make two checks against Fort DC 10+HD of the zombie. If one fails, you turn into a zombie in 1d4 days, if both fail, you turn into a zombie in 1d2 days. In 1d4 hours your base land speed drops by 33%. In 2d8 hours after that, you take a -3 penalty on reflex saves.
This homebrew is meant for an ECL 1 DnD 3.5 zombie survival campaign. I want to know how much I should (or even if I should) change zombie CR by.
EDIT: I will use the zombie plague but with the following modifications:
The infected automatically die in 3d4 days if they don't stave off the disease.
The DC is 10+HD