HIV INFECTION AND AIDS
incidence: common
cause: virus (human immunodeficiency virus) symptoms: sometimes viral illness after infection, but often none initially;
later, weight loss, fever, lymph node swelling, recurrent
infections
treatment: no cure, but medications can slow disease process
The human immunodeficiency virus (HIV) is the virus that causes the acquired immunodeficiency syndrome (AIDS). HIV and AIDS are not the same thing, although people sometimes erroneously use the terms interchangeably. The first reports of people dying from AIDS emerged in the early 1980s, and the understanding that HIV was the cause of this syndrome came soon after. Recently tissue and blood samples from people who lived in Africa in the 1950s have been found to have evidence of the virus, so it appears to have been around longer than was previously thought. No one knows exactly how, when, or where HIV originated.
Two types of HIV are recognized: HIV-1 and HIV-2. There are also some variations among the HIV-1 types,- nine have so far been recognized. HIV-1 is the primary strain seen in all areas of the world except West Africa, where HIV-2 predominates. Only about forty cases of HIV-2 have been reported in the United States, and all of these were among people who had traveled to West Africa or had had sexual contact with someone from West Africa. Nevertheless, in most areas of the United States, testing for HIV usually includes testing for both types of the virus.
The virus infects certain cells of the body, specifically those that have a particular protein, the CD4 protein, on their surface. One cell type, CD4 lymphocytes or T helper cells, is an important part of the immune system, which is the body’s defense system against infections and the development of cancer. HIV is a type of virus called a retrovirus, a term used to describe the process by which it infects a target cell. When the virus attaches to a cell, its genetic material is incorporated into the genetic material of the cell. The infected cell then makes new HIV which can then go on to infect other cells.
When a person is first infected, a large amount of virus circulates in the system, and initially the number of CD4 cells declines; however, the body’s immune system then regains control and suppresses the vims for a period of about ten years. Eventually, however, the virus somehow “outsmarts” the body’s immune system and starts destroying the cells it has infected, a process that makes the infected person very vulnerable to other infections and malignancies. At this point, a person is considered to have AIDS. Why this happens, and why it occurs at different times for different people, is not clear, although genetic differences may determine a person’s susceptibility to infection with AIDS as well as how long it will take the person to develop AIDS if he or she becomes infected.
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