.. f the mouth by the fungus Candida Albicans, is common in the early symptomatic phase of AIDS. Other infectious fungi include species of the genus Cryptococcus, a major cause of Meningitis in up to 13 percent of people with AIDS. Also, infection by the fungus Histoplasma Capsulatum affects up to 10 percent of people with AIDS, causing general weight loss, fever, and respiratory complications or severe central nervous system complications if the infection reaches the brain. Viral opportunistic infections, especially with members of the Herpes virus family, are common in people with AIDS. One Herpes family member, Cytomegalovirus (CMV), infects the retina of the eye and can result in blindness. Another herpes virus, Epstein-Barr virus (EBV), may result in a cancerous transformation of blood cells.
Infections with Herpes Simplex Virus types 1 and 2 are also common and result in progressive sores around the mouth and anus. Many people with AIDS develop cancers, the most common types being B-cell Lymphoma and Kaposis Sarcoma. Kaposis Sarcomaa cancer of blood vessels that results in purple lesions on the skin that can spread to internal organs and cause deathoccurs mainly in homosexual and bisexual men. Although the cause of KS is unknown, a link between KS and a new type of herpes virus was discovered in 1994. Human Immunodeficiency Virus (HIV) The causative agent of AIDS is HIV, a human retrovirus.
Researchers have known since 1984 that HIV enters human cells by binding with a receptor protein known as CD4, located on human immune-cell surfaces. HIV carries on its surface a viral protein known as cp120, which specifically recognizes and binds to the CD4 protein molecules on the outer surface of human immune cells. However, in 1984 researchers found that CD4 by itself was not sufficient for HIV infection to take place. Some other unknown factor, found only in human cells, was also required. After much research, in 1996 scientists discovered that HIV must also bind to Chemokine Receptors, small proteins also found on the surface of human immune cells, to enter the cells. The first Chemokine Receptor linked to HIV entry was CXCR4 (originally called fusin), which is bound by HIV strains that dominate during the latter stages of the disease.
Researchers then determined that another Chemokine Receptor, CCR5, bound HIV strains that dominate in the early stages of the disease. Researchers are continuously discovering more chemokine receptors. Any human cell that has the correct binding molecules on its surface is a potential target for HIV infection. However, it is the specific class of human white blood cells called CD4 T-cells that are most affected by HIV because these cells have high concentrations of the CD4 molecule on their outer surfaces. HIV replication in CD4 T-cells can kill the cells directly; however, the cells also may be killed or rendered dysfunctional by indirect means without ever having been infected with HIV. CD4 T- cells are critical in the normal immune system because they help other types of immune cells respond to invading organisms.
As CD4 T-cells are specifically killed during HIV infection, no help is available for immune responses. General immune system failure results, permitting the opportunistic infections and cancers that characterize clinical AIDS. Although it is generally agreed that HIV is the virus that causes AIDS and that HIV replication can directly kill CD4 T-cells, the large variation among individuals in the amount of time between infection with HIV and a diagnosis of AIDS has led to speculation that other co-factorsthat is, factors acting along with HIVmay influence the course of disease. The exact nature of these cofactors is uncertainit is believed that they may include genetic, immunologic, and environmental factors or other diseases. However, it is clear that HIV must be present for the development of AIDS.
Modes of Transmission HIV is spread through the exchange of body fluids, primarily semen, blood, and blood products. It is most commonly spread by sexual contact with an infected person. The virus is present in the sexual secretions of infected men and women and gains access to the bloodstream of the uninfected person by way of small abrasions that may occur as a consequence of sexual intercourse. HIV is also spread by any sharing of needles or syringes that results in direct exposure to the blood of an infected individual. This method of exposure occurs most commonly among people abusing intravenous (IV) drugs (drugs injected into the veins).HIV transmission through blood transfusions or use of blood-clotting factors is now extremely rare because of extensive screening of the blood supply; it is estimated that undetected HIV is present in fewer than 1 in 450,000 to 600,000 units of blood. HIV can be transmitted from an infected mother to her baby, either before or during childbirth, or through breast-feeding. Although only about 25 to 35 percent of babies born to HIV-infected mothers worldwide actually become infected, this mode of transmission accounts for 90 percent of all cases of AIDS in children.
In addition, even uninfected children born to HIV-infected mothers have an incidence of heart problems 12 times that of children in the general population. In the health care setting, workers have been infected with HIV after being stuck with needles containing HIV-infected blood or, less frequently, after infected blood contacts the workers open cut or splashes into a mucous membrane (for example, the eyes or the inside of the nose). There has been only one demonstrated instance of patients being infected by a health-care worker; this involved HIV transmission from an infected dentist to six patients. In general, infected health-care workers pose no risk to their patients. There is also no risk of contracting HIV infection while donating blood. The routes of HIV transmission are well known, but unfounded fear continues concerning the potential for transmission by other means, such as casual contact in a household, school, workplace, or food-service setting.
No scientific evidence to support any of these fears has been found. HIV does not survive well when exposed to the environment. Drying of HIV-infected human blood or other body fluids reduces the theoretical risk of environmental transmission to essentially zero. Additionally, HIV is unable to reproduce outside its living host; therefore, it does not spread or maintain infectiousness outside its host. No cases of HIV transmission through the air, by casual contact, or even by kissing an infected individual have been documented. Researchers have recently identified a protein in saliva, known as secretory leukocyte protease inhibitor (SLPI), that prevents HIV from infecting white blood cells.
However, practices that increase the likelihood of contact with the blood of an infected individual, such as open-mouth kissing or sharing toothbrushes or razors, should be avoided. There is also no known risk of HIV transmission to coworkers, clients, or consumers from contact in food-service establishments. Studies have shown no evidence of HIV transmission through insectseven in areas where there are many cases of AIDS and large popu Health and Beauty.