Worldwide AIDS epidemic. Conceptual computer artwork of the Earth in the shape of the AIDS (acquired immune deficiency syndrome) virus. The shape of the Earth is that of the virus capsid (protein shell), while the protruding objects are the viral surface proteins. This image represents the worldwide spread of AIDS, particularly in Africa (centre). AIDS is caused by the human immunodeficiency virus (HIV), which has an icosahedral (20-sided) capsid. AIDS was first reported in 1981. By the 1990s, millions were infected worldwide, with infection rates and mortality rates particularly high in sub-Saharan Africa. It is thought that millions more people worldwide will be infected by 2010.