BSE: a global update.

As the British bovine spongiform encephalopathy (BSE) epidemic declines towards extinction, the European epidemic continues to grow. The introduction of active surveillance in Europe and elsewhere makes direct comparison with past events in Britain difficult. BSE is increasingly recognized to be a global problem. While the epidemics in other countries may never reach the scale experienced in Britain, failure to learn from the British experience will prolong consumer concerns and the consequences for international trade for many years. There are still more clinical cases in Britain per year than in any other country. Nevertheless, the risk of exposure of British cattle may for some time have been greatest from imported products. The tightening of British feed controls in 1996 has had a significant effect, but feed controls were only tightened in Europe in 2000 and 2001. The covert nature of exposure means that risks are not recognized until long after the critical event of exposure has occurred. Recent consideration by the European Commission's Scientific Steering Committee (SSC) of the risks of importing BSE suggests that dispersal of infectivity from European countries was wide-spread even before the disease was first recognized in Britain in 1986.