1986: Discovery of bovine spongiform encephalopathy (BSE), commonly called mad cow disease, in cattle in Britain.
1988: British government bans cattle feed containing cow parts and begins destroying BSE-infected cattle. (Eventually 3.7 million cattle are killed.)
1990: British agriculture minister appears on television urging his 4-year-old daughter to eat a hamburger, assuring the public that beef is safe.
1993: Canada reports its first case of mad cow disease.
1996: The British government admits BSE-infected beef may transmit mad cow disease to humans in the form of vCJD, or variant Creutzfeldt-Jakob Disease. (The classic form of CJD previously appeared mostly in the elderly.)
1997: The United States and Canada ban cattle feed containing cow parts.
July 2001: The European Union tightens BSE testing; now, one out of four cows is screened.
September 2001: Japan reports its first case of mad cow disease.
October 2001: Japan begins BSE testing on all cattle slaughtered for human consumption.
May 2003: Despite increased safety measures, scientists discover a single new case of mad cow disease in Canada.
Dec. 23, 2003: The United States reports its first case of mad cow disease in Washington state.
Dec. 30, 2003: The USDA announces new regulations on cattle slaughter, including bans on using downer cattle and mechanically separated meat for human consumption.