When we hear the word “Zombie” we think of gross dead people who have risen from their graves and want to eat our brains.  Popular movies and TV shows such as I am Legend, The Walking Dead, Zombieland, and World War Z have all dramatized and expanded on the Zombie apocalypse, making it a nation-wide interest.  And many people have actually come to believe that such an outbreak amongst humanity can occur.

The H1N1 flu epidemic was so contageous, and deadly, that it created a world-wide scare for many people that the apocalypse could happen.  There are in fact, some diseases that can alter the wires in the human brain, and make them act in an insane and barbaric manner.  One parasite called toxoplasmosa gondii, commonly found in rats, actually invades the brain and forces the rats to do reckless and barbaric acts.  Horrifyingly enough, half the human population actually has these parasites in their body already.  The parasites have not yet adapted to the human host bodies, and have not yet learned how to control the human brain.  But in the future the parasites could very well adapt and make us act like the infected rats.

Another commonly known disease is Mad Cow disease.  Originating in cows, it can be spread to any human who eats the infected meat.  Some side effects are changes in walking, hallucinations, stumbling, muscle twitching, seizures, and a rapid development of dementia.  Now none of these symptoms are violent in any way, but the virus can very easily evolve into something more violent.

So with the current diseases the world currently has, there will not be a mass chaos, full blown, zombie apocalypse.  But who knows, these viruses could very well adapt, and evolve into more violent versions, and humanity could actually face a wide-spread epidemic!

http://www.cracked.com/article_15643_5-scientific-reasons-zombie-apocalypse-could-actually-happen_p3.html