Acquired immune deficiency syndrome, or AIDS, 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 defects may not be apparent for years. They lead in a relentless fashion, however, to a severe suppression of the immune system's ability to resist harmful organisms. This leaves the body open to an invasion by various infections, which are therefore called opportunistic diseases, and to the development of unusual cancers. The virus also tends to reach certain brain cells. This leads to so-called neuropsychiatric abnormalities, or psychological disturbances caused by physical damage to nerve cells.
Since the first AIDS cases were reported in 1981, through mid-1992, more than 190,000 AIDS cases and more than 152,000 deaths had been reported in the United States alone. This is only the tip of the iceberg of HIV infection, however.
It is estimated that between 1 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 health-care providers. HIV infection and AIDS represent one of the most pressing public policy and public health problems worldwide.
Definition of AIDS
The U. S. CENTERS FOR...