Sign up to get free environmental news updates by email. Your brain degenerates, piece by piece. First you feel depressed, then you have trouble coordinating. You lose sight, speech, motor control, as the disease travels through the brain. When it reaches the control centers for breathing or heartbeat, you die.
Medical science has no idea how to cure or even slow it.
Don't get mad. As of last week, nvCJD had killed 79 Europeans. The link between mad cow disease and human CJD is only beginning to be understood. Both appear to be caused by an agent that isn't a virus or bacterium or any previously recognized form of life. It seems to be a simple protein called a prion, though proteins are not supposed to be able to reproduce and go around infecting things.