Source of variant Creutzfeldt-Jakob disease outside United Kingdom.

We studied the occurrence of variant Creutzfeldt-Jakob disease (vCJD) outside the United Kingdom in relation to the incidence of indigenous bovine spongiform encephalopathy (BSE) and to the level of live bovines and bovine products imported from the UK during the 1980s and the first half of the 1990s. Our study provides evidence that a country's number of vCJD cases correlates with the number of live bovines it imported from the UK from 1980 to 1990 (Spearman rank correlation coefficient [r(s)] 0.73, 95% confidence interval [CI] 0.42-0.89, p < 0.001). Similar correlations were observed with the number of indigenous BSE cases (r(s) 0.70, 95% CI 0.37-0.87, p = 0.001) and carcass meat imported from the UK from 1980 to 1996 (r(s) 0.75, 95% CI 0.45-0.89; p < 0.001) Bovine imports from the UK may have been an important source of human exposure to BSE and may have contributed to the global risk for disease.