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Acquired immune deficiency syndrome, or , is a recently recognized disease entity. It is caused by infection with the human immunodeficiency virus (HIV), which attacks selected cells in the immune system (see IMMUNITY) and produces defects in function. These def ....

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.... million and 1.5 million Americans had been infected with the virus by the early 1990s but had not yet developed clinical symptoms. In addition, although the vast majority of documented cases have occurred in the United States, AIDS cases have been reported in about 162 countries worldwide. Sub- Saharan Africa in particular appears to suffer a heavy burden of this illness. No cure or vaccine now exists for AIDS. Many of those infected with HIV may not even be aware that they carry and can spread the virus. It is evident that HIV infection represents an epidemic of serious proportions. Combating it is a major challenge to biomedical scientists and ....