What about sulfur? Sulfur is yellow ... That was actually the first thing that struck me when
Tanya spoke of yellow bones ...
Just an idea: What, if this whole Zombie-stuff is kind of hell let loose on earth? Like kinda doom-style and stuff ... Would explain the outbreak in many parts of the US as well as the world; would explain the deep cracks in the earth; would explain the weird conditions around
ground zero; would explain the bitter and vile evilness everywhere; would explain the different types of zombies (like rooted in different demons and stuff ...).