If you ignore for a second the constant forward-looking attention Internet news demands and stretch your mind back to the Mad Cow Disease scare of 2004, you might remember thinking "how strange that proteins can act as pathogens in the mammalian body!"

Mad Cow scares us because it's an enigma--a protein disease that acts like it has DNA. But now it's looking more familiar, as researchers prove it mutates very much like a DNA or RNA virus or bacteria.