Zombies are a staple in pop culture, especially apocalypse fiction. They come in many forms but none quite like the skels and stragglers in Colson Whitehead's Zone One. Skels are the more typical walkers, with the US Marines assigned to take them out. On the other hand, the stragglers are stuck where they turned, and might not be bloodthirsty like the skels. In both cases, the zombies turned from a virus. A pandemic with New York as the epicenter.
Zombies may be fictional, but pandemics are not. We've never seen a pandemic turn humans into zombies, but is it possible? We never quite know how to predict the next pandemic, but experts agree that slow-walking, flesh-eating humans are not in our path. Coming back from the dead and cannibalistic symptoms are off the table. A disease that creates zombie-like symptoms is more possible. Stephanie Watson, through Harvard Health Publishing, discussed that the highest probably of zombie-like behavior would be spread through toxins. She also suggested it would most likely spread like a typical virus, through bodily fluids like coughs and sneezes.
Current diseases that can give both humans and animals zombie appearances are more common than you think. Confusion, skin changes, loss of motor skills, and flu-like symptoms are all potentials. In a Lewis Gale Physicians article, rabies, Mad-Cow disease, and leprosy are all listed as showing zombie-like symptoms. There is also Cotard’s Syndrome. This is where someone believes that they are either dead or do not exist. It is completely mental, but some may present the neurological symptoms of zombiism. In animals, bizarre behavior like leaving their groups and losing fear of humans are signs of these “zombie” diseases. In dear, elk, and moose, Chronic Wasting Disease makes them weaken quickly and present neurological issues. Other animals with these types of diseases include ants, racoons, and spiders. Read more here and here.