That's accumulated time since 1980. The government fears mad cow disease in the blood supply.
Worried that England's notorious and deadly mad cow disease might make its way into this country, the U.S. Food and Drug Administration is planning to restrict blood donations from people who have spent time in the United Kingdom.
As now written, the FDA's new guidelines will screen out any potential donor who has spent an accumulated total of six months or more in the United Kingdom since Jan. 1, 1980. The country is made up of Great Britain (England, Scotland, Wales) and Northern Ireland.
Mad cow disease, or bovine spongiform encephalopathy, is one of a group of brain-wasting diseases scientists have studied for many years. The brains of infected individuals _ animal or human _ develop numerous small cavities as nerve cells die, producing a spongy appearance. Eventually, and in every case, the central nervous system fails and death occurs.
British farmers just this week celebrated the lifting of a three-year ban on British beef exports imposed by European regulators. The embargo crippled Britain's beef industry, which lost an estimated $2.4-billion in sales.
The ban was lifted when officials ended the practice of feeding cows to cows _ using discarded beef and sheep parts in protein supplements fed to cattle _ and when they believed they had destroyed the infected animals.
But a key feature of the disease is that it sometimes takes many years before it is detected. Visitors to the United Kingdom could have been infected without knowing it by eating infected beef. At home, their donated blood could spread the disease.
By restricting donations from U.K. visitors all the way back to 1980, the FDA hopes to ensure that all the potentially infected people are screened out. The outbreak in Britain began in the mid-1980s.
Dr. Lawrence Schonberger of the Centers for Disease Control and Prevention in Atlanta, a member of the committee that recommended the new restrictions, said the decision was difficult.
As originally drawn up, he said, the new guidelines would have screened out anyone who had visited the United Kingdom for any length of time since 1980.
"We're dealing with unknowns," Schonberger said. "It's purely a judgment thing. If we had screened out everyone who had been in the U.K. for any length of time we would have created a blood shortage."
Blood officials, who have watched U.S. contributions fall since the mid-1990s, are anticipating additional declines and are looking for ways to find new donors.
The Red Cross has estimated that if all visitors to the United Kingdom were screened out, the pool of U.S. blood donors would be reduced by more than 10 percent. The six-month visitation standard is expected to reduce the pool by about 2 percent.
"We still don't know how many people have been affected in the U.K.," Schonberger said. "It (the disease) could still be in a lot of people incubating. But where do you draw the line between a potential risk and a real one? It's hard to make an entirely rational decision, so you make your best guess."
Dr. German Leparc is medical director for Florida Blood Services, the regional blood center serving hospitals in Pasco, Pinellas and Hillsborough counties.
"There is no scientific basis for the new guidelines," Leparc said, "but of course we will follow them. We will just have to find new donors."
The FDA acted, he said, "partly because no one wants to get a call later from Mike Wallace or the St. Petersburg Times asking, why didn't you act when you had all this information?"
Meanwhile, donations nationwide are down about 10 percent since 1994, he said, largely because the World War II generation "is getting too old."
"They were good donors. They were raised in an environment where donating was the patriotic thing to do. The current generation has a different attitude."
Despite the lifting of the export ban in Britain, mad cow disease has not been eradicated in the world. Cases continue to pop up, one Saturday in France, bringing the number in that country to 16 this year.
In 1989 the U.S. banned beef and beef products from any country with recorded cases of mad cow disease. Mad cow disease has not been found in this country, although there have been incidents of a related condition called Creutzfeldt-Jakob disease, or CJD. About one in 1-million people dies each year worldwide from this "classic" form of CJD.
CJD has not been directly linked to beef. However, the disease that killed more than 20 people in the United Kingdom is thought to be a variant. British scientists made the link in 1996, and the European Union banned British beef a week later.
_ Times researchers Cathy Wos and Natalie Watson contributed to this report.
How "mad cow' disease gets into humans
How veterinarians think the disease is transmitted
Sheep: Contract a similar disease
Cattle: Eat feed containing protein from infected sheep
+ Lack of coordination
+ Develops in four to seven years
People: Eat beef or dairy products from contaminated cows, may contract fatal nervous disorder
+ Develops over a long time
+ Degenerates vital parts of the brain
+ Causes dementia
+ Weakens muscles
+ Causes imbalance
Source: Virginia Polytechnic Institute and State University; research by PAT CARR