Mad cow disease is the name often given by the media to the illness bovine spongiform encephalopothy, or BSE. This disease attacks the brain and nervous system in cattle, causing death after anything from about 3 to 8 years. It can be transmitted to humans especially if they eat food that contains brain, spine or digestive tissue from infected cattle. In its human form it is known as variant CJD or Creuzfeld-Jakob's disease - as in BSE, it affects the nervous system and motor skills, and is often fatal.

BSE was widespread in several countries, especially the UK, in the 1980s, mainly because of poor regulations on what could be fed to cattle. In 1989 a ban was imposed on feeding certain animal products to other animals, and the disease was brought under control.

Some people stopped eating beef after the scare, but officially the risk is very low since the regulations were tightened up. However, the disease still exists, in fact there have been recent cases in the US, so the risk may be about to increase.