Acquired immune deficiency syndrome (AIDS), group of diseases that result from infection with the human immunodeficiency virus (HIV). A person infected with HIV gradually loses immune function, becoming less able to resist numerous ailments and cancers, which eventually result in death.
AIDS was first identified in homosexual men in early 1980s, and in 1983 scientists isolated a new human retrovirus that came to be known as HIV. Infected with HIV does not necessarily mean that a person has AIDS. In fact, a person may be HIV-positive for more than ten years without developing any of the illnesses that define AIDS.
The progression from HIV infection to AIDS has several indicators. One measure of the progression is the declining number of CD-4 cells, the major type of white blood cell lost due to HIV infection. More recently the actual amount of HIV in a person’s blood has been used to predict the progression to AIDS, regardless of CD-4 T cell count.
One to three weeks after infection with HIV, most people experience a brief period of flu-like symptoms and a vague feeling of discomfort. HIV reproduces to high concentrations and establishes infections throughout the body. Individuals are thought to be highly infectious during this phase.
Infected individual then enter a prolonged symptom-free phase that can last ten years or more. They remain in good health, although HIV continues to reproduce, progressively destroying the immune system. Eventually, an infected person experiences rapidly falling levels of CD4 T-cells and opportunistic infections that are not life-threatening, a phase that can last upto several years.
Finally an infected person suffers extensive immune destruction and serious illness during a phase that may also last months or years. The immune system fails, and death from severe opportunistic infections and cancers follows.
Death from AIDS is generally due not to HIV infection itself, but to opportunistic infections that occur when the immune system is damaged. Among the more than 25 illnesses that attach people with AIDS are a fungus-caused pneumonia, a bacteria-caused pneumonia, and tuberculosis. Manyu people with AIDS also develop cancers, the most common types being B-cell lymphoma and Kaposi’s sarcoma (KS) a cancer of blood vessels that result in purple marks on the skin.
AIDS is caused by HIV, a human retrovirus. HIV enters cells by binding with a receptor protein know a CD4, located on immune-cell surfaces. The class of white blood cells called CD4 T-cells is the most affected by HIV because they have high levels of CD4. The CD4 T-cells help other immune system cells function. As they are killed during HIV infection, general immune system results.
HIV is spread through the exchange of body fluids such as semen and blood. It is most commonly transmitted by sexual contact. HIV is also spread through unsterilized syringes and needles such as those shared among people abusing intravenous (IV) drugs. Although the routes of HIV transmission are well-know, fear continues of possible transmission through casual contact in a school, workplace, or foodservice setting. HIV does not survive well when exposed to the environment and is unable to reproduce outside its living host. Therefore, it does not maintain infectiousness outside its host.
Worldwide, an estimated 30.6 million people, were living with HIV or AIDS in 2000. About 68 percent of cases were in Sub-Saharan Africa and about 22 percent were in southern and eastern Asia and the Pacific. In Africa and Asia, most people contract the disease through heterosexual contact.
The discovery of HIV as the cause of AIDS was made in 1983, and in 1985 the first blood test for HIV was approved. This test detects the presence of antibodies against HIV, an indication of exposure to the virus. However, for about four to eight weeks after exposure, an individual continues to test negative because the immune system has not yet produced antibodies against HIV. In 1996 an additional blood test was developed that detects HIV antigens, proteins produced by the virus itself.
Because there is no successful vaccination. Against HIV, prevention efforts have focused on educating the public about HIV transmission and personal measures that reduce the risk of infection. Safe-sex campaigns encourage sexual abstinence and the use of latex condoms during sexual intercourse. Needle-exchange programs reduce needle sharing among IV drug abusers. Testing of the blood supply has greatly reduced the risk of contracting HIV from blood products.