4. Mad Cow Disease
I know what you’re thinking, humans cannot get Mad Cow Disease due to the whole not being a cow thing. This is true, however, humans have an equivalent to this disease known as Variant Creutzfeldt-Jakob disease. This disease is caused by something called “prion.” It’s a type of protein that can trigger normal proteins in the brain to fold abnormally. This can actually affect both humans and animals. On top of this, it’s even possible to spread to humans via infected meat products.

This prion disorder of sorts is what triggers the Variant Creutzfeldt-Jakob disease. This is a degenerative brain disorder that leads to dementia and affects people similar to Alzheimer’s disease. The disease will cause memory issues, vision problems, memory loss, depression, loss of the ability to speak, and even sudden, jerky movements. All of this could lead one to believe they are seeing a walking zombie-like figure if they came in contact with a person that had a late-stage version of this.