How aids Affects the Body

AIDS is the final, life-threatening stage of infection with human immunodeficiency virus (HIV). AIDS stands for acquired immunode­ficiency syndrome. The name refers to the fact that HIV severely damages the immune system, the body's most important defense against diseases. Cases of AIDS were first identified in 1981 in the United States, but researchers detected HIV in a specimen collected in 1959 in central Africa. Millions of AIDS cases have been diagnosed worldwide.

Cause. AIDS is caused by two viruses that belong to a group called retroviruses. The first AIDS virus was isolated by researchers in France in 1983 and researchers in the United States in 1984. This virus be­came known as HIV-1. In 1985, scientists in France identified an­other closely related virus that also produces AIDS. This virus, named HIV-2, occurs mainly in Africa. HIV-1 occurs throughout the world.

HIV infects certain white blood cells, including T-helper cells and macrophages that play key roles in the immune system. The virus at­taches to the CD4 receptor molecules on the surface of these cells, which are often called CD4 cells. HIV enters the CD4 cells and inserts its own genes into the cell reproductive system. The cell then pro­duces more HIV, which spreads to other CD4 cells. Eventually, the infected cells die. The immune system produces millions of CD4 cells every day, but HIV destroys them as fast as they are produced.

Symptoms. People infected with HIV eventually develop symptoms that also may be caused by other less serious conditions. With HIV infection, however, these symptoms are prolonged and often more severe. They include enlarged lymph glands, tiredness, fever, loss of appetite and weight, diarrhea, yeast infections, and night sweats.

HIV commonly causes a severe "wasting syndrome", resulting in substantial weight loss, a general decline in health, and, in some cases, death. The virus often infects the brain and nervous system. There HIV may cause dementia, a condition characterized by sensory, think­ing, or memory disorders. HIV infection of the brain also may cause movement or coordination problems.

An HIV-infected person may develop AIDS from 2 to 15 or more years after becoming infected. In children born with HIV infection, this interval is usually shorter. There are six periods in the AIDS course. The first is infection with the virus. The second is incubation and it lasts for 2 or 3 weeks. The third period is the so-called acute AIDS. During this time (2—3 weeks) airway inflammations, allergy, mononucleosis may occur. Then comes the fourth — latent, hidden — period. It's the longest one and can last up to 15 years (usually 2—3 years). The fifth period is pre-AIDS. Its signs are cough, emaciation, lymphoadenopathia, fever, night sweats. The person is to die within 1.5 years. The sixth period is AIDS itself — the person slowly dies of any casual infection or invasion.

Medical treatment can increase the interval by inhibiting the growth of HIV, preserving the immune system, and delaying the onset of opportunistic infections. An infected person can transmit the virus to another person whether or not symptoms are present. Infection with HIV appears to be lifelong in all who become infected.

Transmission. Researchers have identified three ways in which HIV is transmitted: (1) sexual intercourse, (2) direct contact with infected blood, and (3) transmission from an infected woman to her fetus or baby. The most common way of becoming infected is through sexual contact with an HIV-infected person. Most people who have the virus don't even know about it. They may look and feel completely well. To prevent transmission of HIV, sexual contact with anyone who is or might be infected with the virus must be avoided.

People who inject drugs into their bodies can be exposed to infected blood by sharing needles, syringes, or equipment used to prepare drugs for injection. Health-care workers can become infected with HIV by coming into direct contact with infected blood. This may occur through injury with a needle or another sharp instrument used in the treatment of an HIV-infected patient. A few patients became infected while re­ceiving treatment from an HIV-infected dentist and from a surgeon.

An infected pregnant woman can transmit the AIDS virus to her fetus even if she has no symptoms. Transmission may also occur from an HIV-infected mother to her baby through breast-feeding.

Studies indicate that HIV is not transmitted through air, food, or water, or by insects. No known cases of AIDS have resulted from sharing eating utensils, bathrooms, locker rooms, living space, or classrooms.

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