Dead Head's could work for slang... Mad dog works for the infected as well. They are common terms people use.

As to the medical term... Rabid would work as well for the first stage. The second stage, I would just call Zombies. You could look at it this way. The first stage they are infected and that makes them dangerous but they act like rabid animals as they are losing their minds so they aren't actual zombies yet. They are the Rabid.. Or the infected either one.

The second stage is where they become actual zombies and though you know the infection is the first stage of it and is considered part of the zombie cycle... They are not yet into the actual zombie stage. Research Rabies to help with this I think. It is the disease that comes closest to what your talking about as far as behavior is concerned. You can then refer to everyone in the second stage as zombies because that is what they are. Or if you have what you want to name the disease that does this other than the zombie virus, you can name either or both stages in some way after the virus itself.