More than 42 million people around the world are currently infected with human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS).
New HIV infections have leveled off or even declined in most developed countries, but the virus is spreading rapidly through much of the developing world. In some areas of sub-Saharan Africa, one in four adults is carrying the virus.
AIDS was first identified in 1981 among homosexual men and intravenous drug users in New York and California. Shortly after its detection in the United States, evidence of AIDS epidemics grew among heterosexual men, women, and children in sub-Saharan Africa. AIDS quickly developed into a worldwide epidemic, affecting virtually every nation. By 2003 the United Nations Program on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimated that worldwide 40 million people, including 2.5 million children under the age of 15, were living with HIV infection or AIDS.
The WHO, a specialized agency of the United Nations (UN), estimated that from 1981 to the end of 2002 about 20 million people died as a result of AIDS. About 4.5 million of those who died were children under the age of 15. UNAIDS and the WHO reported that 3 million people died in 2003 alone from AIDS, and 5 million more people became infected with HIV.
AIDS has struck sub-Saharan Africa particularly hard. In 2003 one in five adults in this region had AIDS or HIV infection, the highest rate of infection in the world since the epidemic began. Sub-Saharan Africa is the most severely affected region in the world with 26.6 million people living with HIV/AIDS as of 2003.