“Zombie expert Matt Mogk defines a zombie with three criteria: it is a reanimated human corpse; it is relentlessly aggressive, and it is biologically infected and infectious. But Mogk notes that this definition has been altered by the recognition of “rage” zombies, which are infected but still alive,” Smith wrote on a recently published BMJ study.

Smith cited several scientific studies, news reports and fictional works to back up her research. As listed on Discovery News, the author specified three possible pathogens that could cause an outbreak: the Black Plague bacteria Y. pestis, mad cow disease as well as the Cordyceps fungus.

Out of the three pathogens, it is the Cordyceps fungus which is the most common, with 400 known species. According to the publication, the parasitic fungus invades the body of its host and takes over, using the body as a means to make the fungus spores spread.