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Since you described it being similar to The Thing, I read through every example of Body Horror literature page, and came up empty. None of the synopses resembled what you describe, and anything even slightly close didn't have a cover like that. So I don't have any answers for you, but I can pretty safely say it wasn't anything on there.
The Michael Crichton book Prey is about nanomachines, but I can't seem to find the book with a cover like you describe.
Trying to remember (obviously) a book I mostly read maybe 9 or 10 years ago. It was science fiction, and I seem to remember it being sort of like The Thing but in Florida (or some coastal US location), and the infection or w/e it was, was caused by nanomachines (I think). I also seem to remember the cover art having lots of red and blue, and I think it was a x-ray of cross section of a human skull with all sorts of weird machinery attached.
This ringin any bells for anyone?