A zombie virus is actually not that far away. Scientists have discovered a plant deep in the amazone that contains a certain cell that "infects" the brain of organism. On 13th august, american scientist discovered this plant. The cell it contains is very tiny and enters the body via the skin. There it would enter the veins and makes it way to the brain. The cell contains a special enzym that allows it to use the brain for its own purpose. The enzym only reacts to a special enzym that only the human brain has. When the cell "takes over" the brain, it causes to host to get bad headaches, stomach pains and other minor things. After around 2 days, the host gets hallicunations and may become aggresive. The plant is currently under research in an texas research centre. They are currently working on a way to cure or kill the cell taking control. But in end i made everything up and just wasted your time.