LAWRENCE BUELL: My name is Lawrence Buell, from Las Vegas, Nevada, and I want to ask CNN "What is mad cow disease, and what is its effects on humans?"</s>ELIZABETH COHEN, CNN MEDICAL CORRESPONDENT: Mad cow disease is properly known as bovine spongiform encephalopathy, and it was first identified in Great Britain in the 1990s. There's also a human form of mad cow disease, called variant Creutzfeldt-Jakob disease. Now the disease manifests itself very similarly in both cows and humans. It's called a brain-wasting disease. It is gruesome. People lose control of their actions, they lose control of their ability to speak, and mad cow disease always ends in death. There are several things that make mad cow disease particularly difficult. One of them is that, in humans, there's a five to 20-year incubation period, so that means that, once you're infected, you won't feel symptoms probably for the next five to 20 years, and so that makes it very difficult to fight. What if that infected person then gives blood, what if that infected person dies and donates tissue? Those are all very big unknowns as to whether or not that would transmit the disease, and that's currently what federal health authorities are studying. In Europe, 90 people have died, in England, France and Ireland, but in the United States, there haven't been any deaths, and no cattle have been identified with mad cow disease.
Ask CNN: What Is Mad Cow Disease, and What Are Its Effects on Humans?