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 AIDS
is the final, life-threatening stage of infection with human immunodeficiency
virus (HIV). AIDS stands for acquired immune deficiency syndrome. The
name refers to the fact that HIV severely damages the immune system,
the body's most important defence against disease. Cases of AIDS were
first identified in 1981, in the United States, but researchers have
detected HIV in a specimen collected in 1959 in central Africa. Millions
of AIDS cases have been diagnosed worldwide. How AIDS affects the body Cause. AIDS is caused by two viruses that belong to a group called retroviruses. The first AIDS virus was isolated by researchers in France in 1983 and in the United States in 1984. The virus became known as HIV-1. In 1985, scientists in France identified another closely related virus that also produces AIDS. This virus, named HIV-2, occurs mainly in Africa. HIV-1 occurs throughout the world.HIV infects certain white blood cells, including T-helper cells and macrophages, that play key roles in the immune system. The virus attaches to CD4 receptor molecules on the surface of these cells, which are often called CD4 cells. HIV enters CD4 cells and inserts its own genes into the cell's reproductive system. The cell then produces more HIV, which spreads to other CD4 cells. Eventually infected cells die. (Source: World Book) |
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