Do we have this? This is the premise behind a Zombie Apocalypse, that some force is converting normal people into a "them" and making them go crazy and attack uninfected and/or try to convert others, but it uses an agent other than zombies. This conversion can be functionally nearly identical to a zombie apocalypse but substituting another type of creature, like vampires, werewolves or a The Virus / Viral Transformation in general. On the other hand, the conversion may be entirely mental and have no real biological basis. For example, a televised Hypno Ray, powerful Telepath or mystic could Brainwash people into loyal subjects or just releasing a huge Hate Plague. In these cases the "disease" may not be transmissible by person, but by a central person, Hive Queen, Plague Master or machine. This isn't Not Using the Zed Word, which is about not saying zombie, nor Technically Living Zombie, a specific kind of zombie. Film
- The Crazies has a chemical that causes homicidal reactions in roughly half the population.
- Daybreakers has a vampire apocalypse... which succeeded, and the now empowered vampires engage in industrial scale blood farming from comatose humans.
- In The Signal there's the titular signal, a static transmission that floods the TV's in the fictional city of Terminus and causes half the people to go homicidally crazy without making them stupid. Since there's no visual tells, it's essentially impossible for the people who aren't affected to band together.
- Stakeland. A Zombie Apocalypse with vampires.
- In the Underworld setting, the first lycans (werewolves) were hunted and their progenitor imprisoned for the fear that he might cause a Werewolf Apocalypse.
- One episode of Misfits had a girl whose power was to make other teens morally upstanding and virtuous like herself, out of a desire to no longer be rejected for her beliefs. Everyone affected became a polite, chaste, pastel wearing and well spoken young adult. She planed to take her "movement" national and possibly globally, and since her power was sound based might have been transmissible via television. The cast quickly decides this Brainwashing for the Greater Good must stop, but can't get near her because listening to her causes conversion.
Hello, Unknown Troper. You'll need to get known to lend a hand here.