Since 1996, evidence has been increasing for a causal relationship between ongoing outbreaks in Europe of a disease in cattle called bovine spongiform encephalopathy (BSE or “mad cow disease”) and a disease in humans called new variant Creutzfeldt-Jakob disease (nvCJD). Both disorders are invariably fatal brain diseases that are caused by an unconventional transmissible agent. From 1995 through 1998, a total of 38 human deaths in the United Kingdom and one human death in France were attributed to nvCJD. Although there is strong evidence that the agent responsible for these deaths is the same agent responsible for the BSE outbreaks in cattle, the specific foods, if any, that may be associated with the transmission of this agent from cattle to humans are unknown. However, through 1998, bioassays have identified the presence of the BSE agent in the brain, spinal cord, retina, dorsal root ganglia (nervous tissue located near the backbone), and possibly the bone marrow of infected cattle.

Cases of BSE in cattle have been reported almost exclusively (more than 99% as of 1998) from the United Kingdom, but endemic cases of BSE have also been reported in other European countries, including Belgium, France, Liechtenstein, Luxembourg, Netherlands, Portugal, Republic of Ireland, and Switzerland. Most of these latter countries reported their first endemic case of BSE during 1994–1998. The numbers of reported cases, by country, are available on the web site of the Office International des Épizooties. These numbers should be interpreted with caution, however, because of presumed but unmeasured differences in the intensity of surveillance over time and by country.

Public health control measures have been instituted in each country of Europe to prevent potentially BSE-infected tissues from entering the human food chain. The most stringent of these control measures have been applied in the United Kingdom and appear to be highly effective. In addition, strict bans on the use of ruminant protein for ruminant feed, a practice believed to have amplified the spread of BSE in cattle, have been instituted throughout Europe.

The current risk of acquiring nvCJD from eating beef (muscle meat) and beef products produced from cattle in Europe appears to be extremely small (perhaps fewer than 1 case per 10 billion servings), if it exists at all. However, to reduce this possible risk, travelers to Europe may wish to consider either 1) avoiding such beef and beef products altogether or 2) selecting beef or beef products, such as solid pieces of muscle meat (versus beef products such as burgers and sausages), that might have a reduced opportunity for contamination with tissues that may harbor the BSE agent. Milk and milk products are not believed to pose any risk for transmitting the BSE agent.