My ASU project for the last year has been the medical viability for a zombie plague outbreak.
The fungi and viral options are hardly the scary ones, though they do provide a good idea of just how many ways there are to create a zombie. Though a protozoa called Toxoplasma Gondii is a nice little bug that infects cats/rats/humans and mind-controls rats to be fearless of cats. Its estimated that 1 in every 2 people on the planet are infected with it, with varying but mostly benign effects.. Look it up.
The biggest scariest one is Variant Creutzfeld Jakob disease. Normally, by itself, its not terribly sinister, though it does in some cases create a damn near text book zombie.
Wide gait, hunched over appearance, mumbled speech, hallucinations, hyper aggresiveness, lack of food preference (read: eats anything in front of it), among other symptoms. This is an unaltered un-genetically modified version of the prion that causes the disease. There have been successful weaponizations of it in Switzerland and Germany, both which had 100% infection rates and 100% mortality rates when tested on lab mice populations. Mice, which were 96% genetically identical to humans.
Mix that with studies to reanimate dead tissue that have already been done (they took near brain-dead comatose patients, did a procedure on their brains, and after a time 87% of the patients regained consciousness and cognitive function), and you get pretty close to being able to create a from-the-movies zombie.
Even Carleton University's School of Mathematics and Statistics in Canada (the same guys who do viral modeling for the Canadian government) did a projection on a zombie outbreak, and if it did ever happen, with a contagion anywhere even ballpark similar to how it happens in the movies, human kind does not stand a chance.
Mainly because their projections state: "We show that only quick, aggressive attacks can stave off the doomsday scenario: the collapse of society as zombies overtake us all."
And this quick reaction will not happen, because the American public will see them as people, with civil rights, and the right to due process. You cannot go around shooting people just because they are aggressive and insane if they are not armed. They'll attempt to arrest them first, the contagion will spread further in their limp-wristed attempts to quell the problem, and then it will be too late.
Lock and load.