Heya!

For official names, think about something more medical. Something that, like, the CDC might call them. If it were something simple and catchy, there wouldn't be need for informal slang names.

In the initial stage, where they're still alive, I might go with something like they're in the "incubation" stage. The disease is in them and it is terminal, but they are still alive, so they haven't really REACHED the terminal stage. By that logic, the 'reanimation' stage would be "terminal" stage. You might also go with something like Necrosis for the first stage, too, because the body is literally dying even though the people are alive. And then they go into terminal stage, which is the point of death, and...Lazarus? Maybe something to do with Lazarus returning from the dead?

For informal names...how about something really simple like Runners and Rotters? The first because they're fast, agile, etc and the second because they're, you know, rotting.

For the disease itself, go with something ridiculous and Latin and then give it a nickname that average people call it. Encephalitis is a brain disease, so maybe disease of rotting brain? You know how Bovine Spongiform Ecephalopathy (or however it's spelled) is Foot in Mouth disease? Do something like that, would be my suggestion.
-Quaddy

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