There's something in the air, and you definitely don't want to breath it in. Horror movies about viruses and diseases are particularly frightening, because they are among the most plausible situations that could actually happen in real life. This list ranks the scariest movies about virus outbreaks that infect large groups of people.
It can be a bit tricky to distinguish virus outbreak horror movies from zombie films, because often times zombies are birthed from some kind of airborne virus or disease. However, most of the virus horror movies on this list are more about the contagions infecting people than they are the result of the disease. Examples of these films include Viral, Quarantine, and The Happening.
It Follows is probably the best horror movie about a disease. It's kind of tricky to explain the plot if you haven't seen it, so just go ahead and watch the film if it has somehow evaded you up to this point- you definitely won't be disappointed.