I am not a fan of "thinking" zombies. Those who are undead. The zombie virus kills the person, and then the corpse is reanimated, becoming a mindless, there is the rub, eating machine, governed by the virus. The only purpose of the virus is to feed itself and propagate itself. The virus eats to stay alive in its host and attacks others to reproduce itself. That's it, and that's all.

A "rage" virus is a different animal altogether. World War Z is about a rage virus, as I understand it. Here the person does not die, but does become transformed by the virus, which is often depicted as an extreme strain of rabid. Here I will allow for a "thinking" zombie because the person is still the person, albeit so agitated by the rage virus that the person engages in violence to the extreme. Some rudimentary thought would still be clear.

That's it, and that's all.