Since January, mad cow disease in cattle has spread from Britain, across the continent, into eastern Europe. And the human death toll is up dramatically.
"This is an epidemic already," said Dr. David Heymann.
Dr. Heymann of the World Health Organization says 25 people have died of mad cow disease this year the most ever. Most alarming, he says, it's now clear that it take humans at least a decade to get sick after their exposure to infected beef products, meaning the true horror of the disease has yet to come.
"If, as we understand it, this incubation of 10 to 13 years is a minimum, we may be at the beginning of a much larger epidemic," he said.
In the U.S. meanwhile, the firewall against mad cow is based on a simple premise: protect American cows, and you protect humans.
"What we look for in cows is something may be wrong with their brains," explained Linda Detwiler, who heads the USDA task force that checks cattle for any sign of brain disease. "They may walk in circles. They may press their head against a solid object."
This year, the agency is doubling the number of tests performed on cow brains. And while the good news is that no cases of mad cow have been discovered, the disadvantage is the test itself. It limits science to finding the disease years after a cow gets infected.
"The world is actually looking for that test for the live animal. That would be an improvement of what we have now. Not only do you not have to wait until the cow is dead, but you could also diagnose disease earlier in what they call the incubation period," explained Detwiler.
So for scientists, the race is on for a mad cow blood test. At the University of California, San Francisco, Dr. Stanley Prusiner, says a blood test for prions, the infectious agent in animals, could halt the disease in humans.
"If we could, three days before slaughter examine each cow that's about to be slaughtered, then we could eliminate those cows infected with prions," he said.
In essence, eliminate it from cows and you eliminate it from the food chain.
But the greatest unknown in mad cow disease is, how the disease jumped from cow to man. The source is thought to be some kind of food, especially hamburger or sausage. But other foods, like milk and cheese and gelatin, while believed to be unlikely, have not been ruled out.
In Europe, that very uncertainty still makes eating a burger a show of bravado. So far in America, this Independence Day, we are mad cow free.
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