This is not an objective blog, it is not a counter or a definition. It is simply an opinion. That being said here we go.
First and foremost the idea that we know what form the Undead will come in is nonsensical. To assume you know the future is nothing short arrogance and conjecture. Firstly there are no actual zombies, I can prove this by the fact that if there were I would not be here writing this, I would be on my way to my safe location. Now regardless of your idea of the Undead, Solanum, as it is described on this website is very nearly impossible. The main reason being that the body, the human body, needs two things in order to survive: Blood flow and oxygen.
Putting aside food and water, the aforementioned needs are not nonsense or speculation. Without blood flow oxygen is nonexsistant and oxygen without blood flow is pointless. The two systems are dependant on each other. That being said the only way I can see Solanum type Undead is that there is genetic replifaction on a constant cellular level. Meaning that muscles, including the heart and brain, are replified so quickly that muscle death cannot happen. Now you may wonder "well if muscle death affects the heart and brain how can the brain live without the heart?" This is an appropriate question. If the brain controls all functions than without the heart the brain would die, with one exception. If cellular replification happens so quickly that new tissue can be replaced without the heart being needed, then the brain will survive. The idea being that even though the heart no longer functions brain death is inhibited by massive regrowth of tissue, essentially replacing the brain many times over. This concept removes the heart from the equation, if oxygenated blood is no longer required for the brain to function than the heart is no longer needed. This concept also eliminates higher brain function by replacing the brain at such a rapid rate memories cannot be stored at a sufficient rate. Hence removing the "soul" or "essence" of the human, leaving only the lower brain, classified, often times, as the reptilian brain. The reptilian brain serves only three functions: Live, Eat, and Reproduce. Once said person, now refered to as a host, is reduced to such a basic form of exsistance not only are they Undead but they are no longer human. Now some of you will wonder "What else happens?" This is where my scientific knowledge runs dry, all of this is obviously speculation but in this particular instance it's completely up to you, if the disease you envision allows enhanced visions or strength so be it, I've read enough zombie books and seen enough movies to honestly say: "Should it happen, I hope like hell I'm already dead."
Now as to non-Solanum type zombies, there isn't really much to say except that: Pick your disease. Mira Grant has a particularly unique point of veiw when it comes to infestation. But so does Joe McKinney. The reality of it is, like god, we are unable to truly say we understand. There is much we don't know, it far outweighs what we do know. But we can all say this with a great deal of certainty: Whatever happens, it is likely it will be the worst experience any of us can ever imagine, worse than some. The possibilty of an Undead Apoc. will never fade, so long as we seek to destroy each other, life beyond death will always be the objective of many militaries. I will end my tirade/rant with these words: Should it ever happen, may you find your family, may you live to fight back, may you be a rock in the flood, and may we all find mercy. No matter what happens it is the responsibilty of every man, woman, and child to ensure the survival of our species.