When it comes to cows, one in a million - or in the case of US agriculture, one in 100 million - can have enormous impact on farms and ranches, international trade, and the country's diet.
This week the US Department of Agriculture (USDA) will determine whether an animal suspected of having the bovine disease that can be fatal to humans is in fact a "mad cow."
The first US case of mad cow disease (bovine spongiform encephalopathy, or BSE) was discovered in a Canadian-born Holstein slaughtered last December in the Yakima Valley of Washington State.
Since then, the USDA has had to work hard at both its jobs: assuring that the domestic food supply is safe while promoting an industry that constitutes a large part of the US economy.
"It is important to note that this animal did not enter the food or feed chain," says Andrea Morgan, a senior official with USDA's Animal and Plant Health Inspection Service. "USDA remains confident in the safety of the US beef supply."
Until the testing of this particular animal is complete, officials aren't saying where it had been raised or prepared for slaughter.
Since June, the federal government has tested 113,000 cattle. Of those, two tests were initially inconclusive but later showed no evidence of BSE. Last week's inconclusive test is expected to be confirmed one way or the other this week.
The United States is the world's largest producer of beef. Many cows spend their lives in feedlots and milk barns, where it's possible if not always easy to keep track of herds and individuals. But in wide-open spaces in the West, cattle spend much of the year grazing freely, herds intermingling. In any case, animals are frequently sold, and record-keeping is not foolproof.
In all, according to researchers at Iowa State University, these animals represent the largest single segment of US agriculture, generating more than $30 billion a year in direct economic output plus three times that in related economic output.
The public's reactions
Earlier this year, the Harvard School of Public Health found that most Americans were not concerned about getting the human form of mad cow disease. Nor is there any indication that people have shifted from pot roast to tofu burgers as a result of the scare. While pork and poultry are gaining as a portion of their diet, Americans on average continue to eat more than 60 pounds of beef per person a year.
Still, 41 percent of those in the Harvard survey said they weren't very confident in the meat inspection system.
That lack of confidence remains an issue for major importers of US beef as well. A ban on US beef continues in Japan (which had been the largest importer of US beef), despite President Bush's recent appeal to Japanese Prime Minister Junichiro Koizumi.
To bolster confidence here and abroad, the USDA imposed new rules for beef production. Among these: "Downer" cattle (those injured or too sick to stand) may not be used for human food, and slaughterhouses may not use techniques that can mix brain or spinal-cord tissue (the focus of the disease) with muscle meat.
Federal officials also began testing many more cattle for BSE. In Europe, one in four cows meant for human consumption is tested; in Japan all such cows are tested. Until the first case of BSE was discovered in the US 11 months ago, only about one in 1,700 cows here was routinely tested.
While the USDA has taken steps to improve the ways that BSE can be detected and prevented, consumer groups urge the agency to move faster in several areas: a national animal ID program, a ban on risky animal feed, and the mandatory recall of meat from an infected animal.
"While there is probably no risk to the public, lack of mandatory animal identification and mandatory recall, and the absence of a complete ban on specified risk material in animal and human food, leaves consumers and cattle producers vulnerable in many ways if the cow in question is found to have BSE," says Caroline Smith DeWaal, food-safety director of the Center for Science in the Public Interest.
As the latest announcement of a possible BSE case shows, cattle and beef markets are vulnerable too. Cattle prices dropped sharply, as did stock prices for meat companies and restaurants featuring beef (especially fast-food burger chains).
"If there are additional BSE outbreaks in the United States, the impacts will be much more significant," the Center for Agricultural Policy and Trade Studies at North Dakota State University warned earlier this year. "Domestic consumption of beef could decrease more than 20 percent, and U.S. exports would shut down completely. In this case, the domestic price of beef could decrease 26 percent. Prices of slaughter and feeder cattle would decrease accordingly ... which could destroy the U.S. beef and cattle industry."