Initially, witchcraft or voodoo was considered to bring your body to existence. Voodoo sorcerers performed the ritual after which stored these united nations-dead souls in check, for private gain. In those days, they didn’t eat human flesh rather these were an origin of power, control and terror for use through the witch physician in control.
Eventually during the last half a century, the thought of zombies controlled by voodoo was substituted with the greater believable scenario of the brain broken human-like creature aimlessly walking our planet. The thesis was that the viral infection would cause an encephalitis (brain inflammation) which broken the greater cortex- the thinking area of the brain- while causing physical disabilities along with a longing for human flesh. Being bitten by someone infected would obviously transmit herpes.
Think about the Spanish flu of 1918. This deadly flu pandemic infected 500 million worldwide, and wiped out an believed 100 million people. It remains among the deadliest disasters ever. Similarly the Black Dying, the result of a bacteria, wiped out near to 200 million Europeans within the mid-1300s. Pandemics are really the and infections mutate, therefore it is not too hard to make a virus with zombie-producing effects infecting millions.
However, the zombie nowadays has had on another meaning (though, you may still find many believers in the last definitions too). These zombies represent the after aftereffect of some global catastrophe which brings lower the electrical grid and results in social chaos and riots. An excellent volcano, monster earthquake, currency collapse, terrorist attack, nuclear war, faster climatic change, massive solar flare, giant rogue meteor or a number of global pandemics could all cause what preppers call, TEOTWAWKI –“the finish around the globe as you may know it”.