AIDS stands for acquired immunodeficiency syndrome, a pattern of devastating infections caused by the human immunodeficiency virus, or HIV, which attacks and destroys certain white blood cells that are essential to the body's immune system.
   When HIV infects a cell, it combines with that cell's genetic material and may lie inactive for years. Most people infected with HIV are still healthy and can live for years with no symptoms or only minor illnesses. They are infected with HIV, but do not have AIDS.
     After a variable period of time, the virus becomes activated and then leads progressively to the serious infections and other conditions that characterize AIDS. Although there are treatments that can extend life, AIDS is a fatal disease. Research continues on possible vaccines and ultimately a cure. For the moment, however, prevention of transmission remains the only method of control.