Acquired Immune Deficiency Syndrome (AIDS)
Kategorie: Biológia (celkem: 966 referátů a seminárek)
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- Přidal/a: anonymous
- Datum přidání: 05. července 2007
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Acquired Immune Deficiency Syndrome (AIDS)
Acquired Immune Deficiency Syndrome (AIDS), disease that renders the body's immune system unable to resist invasion by several microorganisms that cause serious infections. It is usually characterized by severe weight loss and fatigue, and frequently by neurological complications due to damage of cells of the brain. There is also a high incidence of certain cancers, especially Kaposi's sarcoma, which shows up as purple lesions on the skin, and tumors known as B-cell lymphomas. AIDS is transmitted by blood, through intimate sexual contact, from infected mothers to their babies in the uterus, and perhaps through infected mother's milk. Before a reliable test for screening blood was developed, a major route of transmission was through receiving transfusions of contaminated blood. A major means of transmission and spread of the virus is through the use of blood-contaminated needles by intravenous drug abusers. Casual contact in general is not a risk factor for infection, and blood donors are definitely not at risk of catching the disease. The virus usually remains dormant for some time in infected T cells, and it may take up to 10 years for symptoms to develop.Several strains of the AIDS virus have been isolated, and it appears to be continually changing in genetic makeup and, thus, its envelope, against which a person's immune system can make antibodies. This makes development of a vaccine that is able to raise protective antibodies to all virus strains a very difficult task. Nevertheless, dramatic progress has been made in a very short time in identifying the molecular makeup of the AIDS virus, its modes of transmission, and the mechanisms by which it produces disease.
Much research centers on solving the problems of treating people who already have AIDS and those who have been infected with the virus but have not yet developed the syndrome. The first chemical shown to be partially effective in reducing clinical symptoms and controlling viral replication, zidovudine, formerly called azidothymidine (AZT), was developed in 1986-87. The fatality rate from AIDS indicates that few, if any, individuals with AIDS are likely to survive in the long run, until some adequate treatment is developed.
AIDS raises many legal, ethical, and civil rights issues.
Among these are mandatory testing of all citizens or of particular populations (for example, marriage license applicants); discrimination in housing, employment, and medical treatment; and confidentiality versus notification of sex partners.
The first case of AIDS was identified in New York in 1979. The cause of the disease, a retrovirus now called Human Immunodeficiency Virus (HIV; see HTLV), was identified in 1983-84 by scientists working at the National Cancer Institute in the United States and the Pasteur Institute in France. These workers also developed tests for AIDS, enabling researchers to follow the transmission of the virus and to study the origin and mechanism of the disease. Close relatives of the AIDS virus infect some African monkeys. This fact and the high incidence of infection of people in central Africa has led to the opinion that the AIDS virus originated there. In 1990, the World Health Organization announced that 203,599 cases of AIDS were reported worldwide by the end of 1989, and estimated the actual number of cases to be 600,000.