The BMJ (British Medical Journal) has posted their annual Christmas research paper: "Zombie infections: epidemiology, treatment, and prevention." It is an exhaustive study of the current zombie outbreak, with plenty of references.
The Solanum virus is the most extensively studied infectious cause of reanimated zombies.7 8 9 It has caused outbreaks around the world but does not have an identified reservoir in nature.8 It has a 100% mortality rate, and zombification is certain in anyone exposed to an infected person. Solanum infection is universally fatal in all animals tested or observed, indicating that zoonotic transfer to humans is an unlikely origin.8 One anecdotal report linked infection to the looting of underwater settlements in the Three Gorges Dam in China.9 A child emerged, bitten, but his fishing partner did not surface at all. The dam was created by relocating over 1.24 million residents and flooding their former villages.10 Zombie expert Max Brooks thinks that Solanum virus infection has occurred for thousands of years and is now emerging because of urbanisation and the interconnected nature of commerce and travel.8 Whether this virus is the cause of the current outbreak in the United States has not been tested.11 12
The caption for the above picture is "2002 outbreak of rage zombies in the UK.15" You can read the entire paper at the BMJ. -via reddit science, where joke comments are forbidden. Commenters are having a hatrd time responding to this one. The BMJ publishes this kind of Christmas paper every year.