lore
To be original, the infection eventually leads to the infected losing their jaw. It spreads through scratches, and the scratches lead to rashes. The rashes are just a byproduct of what’s going on inside, as the skin peels back from the location of the scratch to reveal a coating of bark over the bone. Eventually, the rash completely overtakes the body, resulting in what you see above. Think of it like your skeletons trying to get out of it’s meat prison called skin. Afterward, your intellect would be replaced with instincts that make you want to spread and consume, but the thing that makes twigs, twigs, is that they grow smarter. Some just use their intellect to outsmart people to get to them, but some would do more. Read, learn, try to become a human again, and eventually moving beyond.

The twigs are the philosophers of the zombie world