It seems to inflict completely randomly, and apparently kills me incredibly fast. I assumed it was madness, so I spent the madness in the research tree, and I'm sitting at 0 madness and am still getting it. Its so fast, I die before I even realise my health is draining, usually when i'm running around my workshop crafting stuff.

I don't know what it's called, since again, It takes me by surprise and I don't actually have enough time to mouse over to see what it is. The icon looks like a head, blue on one half, and a red skull on the other.