One estimate is 10 to 15 years, based on the assumption that the initial cases of vCJD stemmed from the earliest BSE outbreak, which began in the early 1980s and peaked in 1992. Such an incubation length would yield only several hundred vCJD cases, according to a study by epidemiologist Neil M. Ferguson and his colleagues at the University of Oxford. But 136,000 deaths are possible. This would make it unusual, but it cannot be ruled out. Complicating the issue is the unknown lethal dose.
Most researchers assume that the more infected beef eaten, the greater the risk.
But the type of beef also matters. Processed meats such as sausage may be the riskiest, because they are more likely to contain bits of brain and spinal cord, where prions abound. Genetics also plays a role. All vCJD patients thus far have had a particular variation on their prion gene, one that occurs in 40 percent of the Caucasian population. In fact, the Oxford estimates consider only these people.