AIDS was first reported in 1981 in the United States and has since become a major epidemic, killing nearly 12 million people and infecting more than 30 million others worldwide. The disease is caused by HIV, a virus that destroys the body's ability to fight infections and certain cancers.

Dr. Richard Morgan, of the National Human Genome Research Institute's Clinical Gene Therapy Branch, defines human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS).

Related terms: cell, retrovirus.