Originally Posted by Nyes the Dark
An interesting idea (not my cup of tea, but it's your group), since it plays with some variation.
My confusion is with the virus zombies. If any open wound caused by a virus zombie can cause zombism, any hit on your PCs would likely end with the others killing him/her and burning the corpse, because otherwise your screwed.
End result: The highest PC mortality rate since Hunger Games.
Unless it is a very small chance or there is some treatment?
If you were doing it in dnd 3.5, you could say a Remove Disease/Break Enchantment (or something expensive like Raise Dead) can cure it before incubation completes... but those are really rare/expensive, and just not feasible to heal everyone this way. It gives the PCs a resource (spells/day, Diamond Dust, Wands/Scrolls) which will quickly deplete if they're reckless, will last them if they don't get hit, and is very valuable among survivors.
The relative value and rarity of the cure could lead to some very good survivor-encounters, as some people try to kill the PCs for it (complete with some sad story about their wives/daughters being infected), and others try to bargain or appeal to their humanity, raising a number of moral questions in the proces. The PCs still have to make that choice, and face the consequences later.