Statistics linking death and the variant Creutzfeldt-Jakob disease (vCJD) from eating BSE infected meat may not be as startling as once believed. Researchers from Imperial College, London, predict this week that as few as 40 people over the next 80 years could die from vCJD as a consequence of eating BSE infected meat.
Previous estimates of the size of the vCJD epidemic have been uncertain, with the estimated upper limit of cases in the UK as high as 50,000 only two years ago. These new predictions are more confident, with a comparable worst-case scenario of 540 UK cases between now and 2080.
Dr. Azra Ghani, who carried out the work with other researchers from Professor Roy Anderson's department, writes : "Our results suggest that the vCJD epidemic will continue to decline with a best estimate of only 40 future cases." These are expected within the next five years.
The group has also come up with a meaningful estimate for the incubation time of vCJD - 12.6 years. This is a similar to the incubation period of Kuru, the related disease that affected people in Papua New-Guinea after they ate the brain tissue of infected individuals.
The researchers used a statistical model based on the annual number of cases of vCJD seen in the UK and the levels of exposure to infected cattle. The updated predictions resulted from including the 17 cases from 2002 in the calculation.
These estimates only consider those people who will catch vCJD from infected beef or beef products. They do not include any cases arising through secondary transmission, for example via surgical equipment that had previously been used on an infected patient.
"The development of a diagnostic test that is able to detect infection early in the incubation period and that can be used to reduce the risk of secondary transmission remains a high priority," added Ghani.
In addition, the scientists only calculated how many deaths would occur among the group of people who are most susceptible to catching the disease. Two natural variants of the prion protein gene exist, one of which seems to confer a higher risk on the individual of catching vCJD. The most susceptible group of people carry two copies of this variant - which equates to about 40 per cent of the Caucasian population.
To date, there have been 129 cases of vCJD in the UK. The average age of disease onset is 26, with death occurring, on average, two years later.
The scientists predictions were published in a recent issue of BMC Infectious Diseases 2003 3:4 (published 27 April 2003).