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BSE a Decade on

An informal explanation is given of the probabilistic risk techniques that were applied immediately after the announcement by the Secretary of State for Health in 1996 of a possible link between bovine spongiform encephalopathy (BSE) and the human form, variant Creutzfeldt-Jakob Disease (vCJD). An up-to-date prediction of vCJD numbers, made using a simplified model, is shown to conform closely with previous predictions, all of which receive strong validation from the human data accruing over the past decade. Government did not act on the risk-based predictions presented at the time and the political lessons for the future are considered for policy areas subject to risk. The biggest food scare in the UK's history was triggered on 20 March 1996 when Stephen Dorrell, Secretary of State for Health, announced to the House of Commons that there was a possible link between BSE and the human form, vCJD. BSE, or "mad cow disease", killed the animal by attacking the brain, causing confusion and loss of limb coordination before death. The first cow had been diagnosed positively with BSE in November 1986, and this prompted the question of whether the new disease could be passed to humans eating beef. There was encouraging evidence from scrapie, a similar infection affecting sheep, which appeared not to have had any adverse effect over the years on humans eating lamb and mutton. Nevertheless a series of countermeasures was introduced in the late 1980's to protect the beef-eating public. Then in 1990 the Creutzfeldt-Jakob Disease (CJD) Surveillance Centre was set up to look for changes in the incidence of CJD, a brain-wasting disease with similarities to BSE, from which about fifty middleaged and old people died each year in the UK. In 1996, after five years of searching, the unit reported to the Secretary of State for Health ten CJD deaths that were unusual because they involved young people, in their twenties. These cases formed the basis of the statement to Parliament in March that year. The Secretary of State made the point in his speech that the risk to humans was "remote", but he did not quantify that adjective: did he mean one in a million or one in a thousand or what? The Government's Spongiform Encephalopathy Advisory Committee (SEAC) presented the view1 that the risk could have been as high as one in a hundred, suggesting that half a million people might die. The result was the biggest food scare that the UK has seen to date, and one that would last for the best part of a decade. A montage of newspaper front-pages shows the prominence afforded the "mad cow" story over many years (Figure 1). It was also the most expensive food scare, costing the taxpayer around £1 bn per year2 from 1996 onwards. This article will examine if the very large sums Figure 1: Newspaper headlines for BSE and vCJD.