I greatly enjoyed my first playthrough of that. Without knowing much of what you guys have discovered, it definitely reminds me of the backstory of a character from I believe one of the Outbreak games, bear with me because this was over a decade ago.
In one of the titles, there was a man who, upon exposure of the virus, didn't die, instead he slowly sort of rotted away while keeping his consciousness and awareness. Unfortunately it ate away at his psyche and kept hunting people down to infect the same way he was, through a plant like the one in the Umbrella labs. Keep in mind this guy was infected from like, before RE1, and survived until right before the city was destroyed.
The vibes I got from the demo was a possible tiny-scale outbreak that, instead of say being a zombie virus, instead slowly mutated a group of people over almost a generation