Acquired immune deficiency syndrome (AIDS) is a fatal disease that attacks the body's immune system, making it unable to resist infection, and is caused by the human immunodeficiency virus (HIV), which is communicable in some bodily fluids and transmitted primarily through sexual behaviour and intravenous drug use.

Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth Centruy. It is now a global epidemic. UNAIDS and the World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first discovered on December 1, 1981, making it one of the most destructive pandemics in recorded history. In 2005 alone, AIDS claimed between an estimated 2.8 and 3.6 million, of which more than 570,000 were children.

Worldwide, five people between the ages of 10 and 24 are infected with HIV every minute.