New variant Creutzfeldt-Jakob disease: the epidemic that never was

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Abstract
In 1996 a new variant of Creutzfeldt-Jakob disease was described and tentatively linked to bovine spongiform encephalopathy as a possible cause.1 Since then a number of studies have been undertaken in an attempt to confirm ingestion of the prion that causes bovine spongiform encephalopathy as the cause of new variant Creutzfeldt-Jakob disease. What was initially a speculation has now evolved into orthodoxy among the medical profession in the United Kingdom if not the whole of Europe, although in the United States the question of causality remains more open.2 Epidemiologists use certain criteria to assess the likelihood of a link between cause and effect for disease. When these criteria are applied to the case for new variant Creutzfeldt-Jakob disease being caused by the bovine spongiform encephalopathy prion the evidence seems weak. Such study also raises the question of whether this is a new disease, as the hypothesis of the infectivity of the bovine spongiform encephalopathy prion to humans and the novelty of the condition are inextricably linked. In this paper I examine the evidence for a causal link between new variant Creutzfeldt-Jakob disease and the bovine spongiform encephalopathy prion and argue in favour of the alternative hypotheses that the variant is not caused by the prion and is not new. #### Summary points The causal link between the bovine spongiform encephalopathy prion and new variant Creutzfeldt-Jakob disease is open to question Assessment of the evidence against relevant epidemiological criteria reveals the weakness of the case for a link The rate of growth in the number of cases is very much less than would be expected from a foodborne source The rate of growth is consistent with a previously misdiagnosed but extremely rare disease being found—this could have resulted from the improved ascertainment of all possible cases of Creutzfeldt-Jakob disease that has been …