HIV, or the human immunodeficiency virus, is the cause of AIDS. The number of people infected with HIV is staggering -- more than 33 million worldwide have the disease, according to the latest estimates from the United Nations. And "more than 25 million people have died of AIDS since 1981," said David Bryden, spokesman for the Global AIDS Alliance Fund, an organization based in Washington, D.C. Established by the World Health Organization in 1988, World AIDS Day serves to focus global attention on the devastating impact of the HIV/AIDS epidemic. The day provides an opportunity for governments, national AIDS programs, faith organizations, community organizations and individuals to demonstrate the importance of the fight against HIV/AIDS.