(CNN) -- Here's a look at what you need to know about Mad Cow Disease, a transmissible fatal brain disease found in cattle.
Facts: It has been linked to a fatal brain disease in humans called variant Creutzfeldt-Jakob disease (vCJD).
The official name of mad cow disease is bovine spongiform encephalopathy (BSE). BSE lesions are characterized by sponge-like changes seen under an ordinary microscope.
Eating contaminated meat or other products from cattle (excluding dairy products) with BSE is thought to be the cause of vCJD.
BSE is passed between cows through the practice of recycling bovine carcasses for meat and bone meal protein, which is fed back to other cattle.
Both mad cow disease and variant Creutzfeldt-Jakob Disease (vCJD) are fatal.
Symptoms of vCJD involve psychiatric symptoms and behavioral changes, movement deficits, memory disturbances, and cognitive impairments.
BSE Statistics (Cattle): (source: CDC) Through April 2012, 23 BSE cases in North America have been confirmed, 19 cases in Canada, and 4 in the U.S. One of the infected cows that died in the U.S. was born in Canada.
Through the end of 2010, more than 184,500 cases of BSE had been confirmed in the United Kingdom in more than 35,000 herds.
vCJD Statistics (Humans): (source: CDC) 1996-2012 - 227 vCJD cases have been reported in 12 countries: United Kingdom - 176 France - 27 Ireland - 4 U.S. - 3 Spain - 5 The Netherlands - 3 Portugal - 2 Canada - 2 Italy - 2 Japan - 1 Saudi Arabia - 1 Taiwan - 1
Timeline: 1986 - Mad cow disease is first discovered in the United Kingdom. From 1986 through 2001, a British outbreak affects about 180,000 cattle and devastates farming communities.
January 1993 - The BSE epidemic in Britain reaches its peak with almost 1,000 new cases being reported per week.
1996 - The first case of variant Creutzfeldt-Jakob Disease is reported.
1996 - 1999 - The European Union bans British beef. France continues the ban for three more years, on the grounds that British beef is not safe.
May 20, 2003 - Canada's first case of mad cow disease is confirmed in an 8 year old cow in Alberta, Canada. Canadian officials say the cow did not enter the food chain.
May 21, 2003 - Mexico, Japan, and South Korea join the United States in temporarily banning Canadian beef. The U.S. lifts the ban in March.
December 23, 2003 - The first case of mad cow disease in the U.S. is confirmed by the U.S. Department of Agriculture. The infected cow is discovered on a farm in Washington State in early December. Japan, China, and South Korea stop the importation of U.S. beef. The infected cow was born in Alberta, Canada, in April 1997 - just four months before the United States and Canada began banning the use of brain and spinal cord tissue in cattle feed.
December 30, 2003 - The USDA announces that the beef from downer cattle will no longer be allowed in the human food chain.
January 9, 2004 - The USDA says it will begin destroying about 130 cattle that were "herd mates" of the cow that tested positive for the first-ever U.S. case of mad cow disease - to make sure none of those cows enters the human food chain.
January 26, 2004 - New safeguards against mad cow disease are announced by the Food and Drug Administration. They include banning chicken waste from cattle feed and barring restaurant meat scraps from being used in animal feed.
January 28, 2004 - The Commodity Futures Trading Commission launches an investigation into whether some commodity futures market players may have known about the first U.S. case of mad cow disease before it was announced to the public.
June 20, 2004 - Charlene Singh, the first person known to live in the United States with variant Crutzfeldt-Jakob Disease, dies.
January 2, 2005 - Canadian health authorities confirm that test results have identified a 10-year-old dairy cow in Alberta as having mad-cow disease. This is Canada's second case of bovine spongiform encephalopathy (BSE) in two years.
June 24, 2005 - The second U.S. case is confirmed by British tests.
March 13, 2006 - The third American case is confirmed after an Alabama cow tests positive.
September 5, 2008 - Canadian scientists announce a discovery that paves the way for diagnostic testing of live cattle, rather than postmortem.
September 13, 2008 - An Alabama research study shows that mad cow disease can sometimes be caused by genetic mutations.
March 10, 2009 - An anti-malaria drug known as quinacrine, which had reportedly shown promise against mad cow disease, is found to have no affect on the disease according to a British medical study.
March 14, 2009 - U.S. government permanently bans the slaughter of cows too sick or weak to stand on their own, seeking to further minimize the contraction of mad cow disease.
March 28, 2009 - Mad cow research pathologist Antonio Ruiz Villaescusa of Spain dies from mad cow disease.
April 24, 2012 - The USDA confirms the fourth case of BSE, found in a dairy cow from central California. The announcement maintains that the cow was never presented for slaughter for human consumption and poses no risk.
May 2, 2012 (update for April 24, 2012) - The California Department of Food and Agriculture (CDFA) identifies the two offspring born to the positive cow in the last two years. One was stillborn. The other was sampled for BSE. The test results were negative.