Sc0ut: I'm glad you further clarified your reaction: makes more sense now!
For what it is worth, what I take from the story so far is that the rash disease has, if not an actual thinking conscious mind, at the least some kind of tropism-level awareness which subsumes and overwhelms the consciousness of the infected organism, controlling the actions of the host but perhaps not completely extinguishing the mind and spirit, leaving the victims to be carried along helplessly in their bodies. That must feel like several kinds of hell, especially if the human or animal infected has occasional moments of clarity. Hence the cries of 'Help me!', the screaming in the airwaves, the dog turning aside from savaging Emil.
Perhaps it is a sliding scale of awareness, with at one end the sort of tropic reaction one sees in the zombie ants of our worlds' Amazon forests, where ants infected by the fungus, once the mycelial threads enter their brains and nervous systems, abandon their usual safe, shaded concealment on the forest floor and instead climb a tall grass stem to which they attach themselves by their jaws, and then die, exposed to the wind which will spread the spores of the fungus to other ants. At the other end of the scale, we have Sleipnope remembering Lalli, and taunting him with his helplessness during the first attack.
We have, as yet, no idea in-story of the precise nature of the disease organism, or of the way it works. My guess would be either some sort of experimental medical treatment gone horribly wrong, or a parasite, or even a symbiont, trying to colonise a type of organism to which it is not quite suited.
Maybe the resurgence of magic in the world has something to do with this? Who knows?