good news? If a mathematical projection is correct, the number could soon peak.
Since the emergence of a new human disease linked to eating beef from cattle with "mad cow" in 1996, the British public has been seized by a question: How bad will the epidemic? Hoping to dispel the confusion, two teams of scientists have refined their projections -. And they come to different answers
Although humans consumed about 750,000 cattle infected with bovine spongiform encephalopathy (BSE) between about 1980 and 1996, no one knows how many people have been infected, or how long it takes for an infected person to get sick. At the end of September 01, 107 people in the UK died from variant Creutzfeldt-Jakob disease (vCJD), an invariably fatal neurodegenerative disease. How many more are at risk is uncertain; the most authoritative estimate to date, the epidemiologist Roy Anderson Group at Imperial College in London, provides a few hundred to a maximum of 136,000.
A new mathematical analysis by researchers at the London School of Hygiene & Tropical Medicine provides encouraging news. The study, published online by Science on 25 October, concluded that the epidemic could be almost its peak. The team used an approach called "back-calculate" which focuses on a smaller number of assumptions, including speculation on the number of people infected with BSE when they were infected, and the incubation time. No matter how these parameters vary, the upper limit of the event is "less than 10,000," said London School epidemiologist statistical Simon Cousens, a co-author.
But those hopes are challenged by the Anderson Group. His newly completed analysis, but still unpublished uses different mathematical techniques and comes with maximum estimates that are "substantially higher," said Neil Ferguson member of the team. Both teams agree that their model may be too optimistic if a key assumption turns out to be false: that all victims of vCJD will share the same genetic profile. While this has been true for all cases of vCJD to date, a number of researchers believe that other genetic profiles may also be sensitive.
Given the lack of reliable tests for the infection of BSE in humans, it is surprising that different mathematical models produce different results, researchers say. Modelers are based on arbitrary assumptions, says epidemiologist Peter Bacchetti of the University of California, San Francisco. But because the London School predicted that the epidemic may soon peak, their projections may be in the short term more testable. Said veterinary epidemiologist Mark Woolhouse of the University of Edinburgh in Scotland: "We will soon know if they are right"
Related Link
Spongiform Encephalopathy Advisory Committee.
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