Bovine spongiform encephalopathy (BSE) is a new prion disease that was firs
t identified in the United Kingdom in 1987. Its appearance was likely cause
d by changes in the rendering process used to produce a meat and bone suppl
ement for cattle, changes that allowed this prion to enter the bovine food
supply. Despite measures that were made to reduce the risk to humans, a new
variant of Creutzfeldt-Jakob disease appeared in the mid-1990s and has bee
n linked to BSE. Although the extent of the disease's impact on humans is n
ot yet known, current estimates predict that there will be 136,000 cases of
this fatal disease by the year 2040. The risk to humans of medications pro
duced with bovine materials, gelatin, and blood transfusion is unknown.