The Star-Ledger (Newark, NJ)

Sweating Blood Over Mad Cow Disease

by Howard Fienberg
February 6, 2001

So, you just got back from Europe. A horrible disease has everyone there afraid to eat beef, but you paid it no mind. Suddenly, your child is in an accident -- she needs a blood transfusion, fast. The doctor informs you that offering your own blood in transfusion is a risky proposition, since you might carry this beef-related disease, which might possibly be blood transmissable. What do you do?

You would need to understand how to balance competing risks. All of us now face a similar problem at the national level. We must balance the risk of further reducing the nation's already short blood supply versus the risk that infection by the human version of mad cow disease, new variant Creutzfeldt Jakob disease (nvCJD), might spread through blood.

No trace of the disease has ever been found in the United States. But travelers to Western Europe just might have consumed contaminated beef, which just might cause nvCJD in humans, which just might be conveyed via their bloodstream into the American blood pool, which just might lead to infection in people who need transfusions.

The nation's blood supply is in a continual crisis. Although 60 percent of the population is eligible to donate blood, only about 5 percent do.

Last year, the Food and Drug Administration (FDA) banned Americans who have spent more than six months in Britain between 1980 and 1996 from donating blood, eliminating 2.2 percent of possible blood donors. Now, at the prodding of the Red Cross, the FDA is considering expanding the ban to all of Western Europe and broadening the timescale from 1996 to the present day. The FDA’s expert panel recommended that the European ban include anyone who had lived there more than 10 years, instead of the Red Cross’ suggested timeframe of six months.

Are we making a sound risk trade-off?

Dr. Adriano Aguzzi of Zurich University has said “research has certainly not proven that blood is infectious.” And a special council of the American Medical Association reported in the summer of 1999 that “epidemiological studies show no evidence that transmission can occur through blood.”

So is there any risk? If so, it is probably low: About 88 people out of 370 million Europeans [presumably beef-exposed] have demonstrated symptoms of the disease. If the disease lives up to its media hype, these victims could just be the tip of the iceberg. But an Oxford University research team projected on August 10 that the maximum number of Britons who could be afflicted with nvCJD must be less than 139,000, and there could be as few as one hundred or less cases. While these are only projections, they depict a relatively limited threat to public health.

Because the risk of nvCJD to the blood supply is theoretical, deciding who should be barred from donating blood becomes problematic. With the bovine version of mad cow disease now nearly eliminated from the British landscape, when can we mark a cut-off for the risk there? This most recent FDA policy proposal resulted from the recent small outbreaks of mad cow across Europe, but what happens when mad cow cases reach other countries? Should we perhaps ban donors who have been anywhere outside North America? The precautionary principle, invoked to justify destroying a significant part of the nation's blood cache, dictates that it is better to be safe than sorry. But risks must be balanced. Rejecting one risk tends to present a half dozen others in its place.

Richard Davey, former chief medical officer for the American Red Cross, was critical of the last decision on British blood donors: “It's likely ... that taking this step in the face of a theoretical risk may actually decrease the safety of the blood supply.” According to the National Blood Data Resource Center, the demand for blood is increasing by 1 percent per year, while donations are decreasing at nearly the same rate. New donors to fill the gap could carry diseases more definitively risky than nvCJD. But more importantly, finding those replacement donors is difficult and extremely expensive.

The FDA is wary of repeating past mistakes with the blood safety, like the spread of AIDS, so they will take the route of caution. But caution should derive from the assessment of cost and benefit, not the arbitrary elevation of little-known risks to overwhelming importance.

The FDA faces some tough questions. If a case of mad cow were one day found in the United States, would they ban all blood donations? At what point do they draw the line between vague possibilities and concrete probabilities?

Howard Fienberg is research analyst with the Statistical Assessment Service (STATS), a nonprofit nonpartisan think-tank in Washington, D.C.


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