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Acquired Immune Deficiency Syndrome

Source: Centers for Disease Control and Prevention; www.cdc.gov

AIDS (Acquired Immune Deficiency Syndrome) is caused by the human immunodeficiency virus (HIV). HIV kills or disables crucial cells of the immune system, progressively destroying the body's ability to fight disease.

HIV is commonly spread through unprotected sexual contact with an infected partner. It is also spread through contact with infected blood. Where modern screening techniques are used it is rare to contract HIV from transfusion, but it can be contracted when intravenous drug users share syringes with others. Though HIV can be spread through semen, vaginal fluids, and breast milk, there is no evidence it can be spread through saliva. The rate of transmission from a pregnant woman to her infant is about 25% without treatment, but can be reduced to less than 2% with treatment. Studies have indicated no evidence of HIV transmission through casual contact such as the sharing of food utensils, towels and bedding, telephones, or toilet seats.

Some people experience flu-like symptoms a short time after infection with HIV, and scientists estimate that about half of those infected with HIV develop more serious, often chronic symptoms within ten years. Even when symptoms are not present, HIV is active in the body, multiplying, infecting, and killing CD4+ T cells, or "T-helper cells," the crucial immune cells that signal other cells in the immune system to perform their functions.

The term AIDS applies to the most advanced stages of HIV infection. According to the official definition set by the Centers for Disease Control and Prevention (CDC), an HIV-infected person with fewer than 200 CD4+ T cells can be said to have AIDS. (Healthy adults usually have 1,000 or more). An HIV-infected person, regardless of T cell count, is diagnosed with AIDS if he or she develops one of 26 conditions that typically affect people with advanced HIV. Most of these conditions are "opportunistic infections" that occur when the immune system is so ravaged by HIV that the body cannot fight off certain bacteria, viruses and microbes.

Months or years prior to the onset of AIDS, many people experience such symptoms as swollen glands, lack of energy, fevers and sweats, and skin rashes. People with full-blown AIDS may develop infections of the intestinal tract, lungs, brain, eyes, and other organs, with a variety of symptoms, and may become severely debilitated. They also are prone to developing certain cancers, especially those caused by viruses, such as Kaposi's sarcoma, cervical cancer, and lymphoma. Children with AIDS may have delayed development or failure to thrive.

HIV is primarily detected by testing a person's blood for the presence of antibodies (disease-fighting proteins) to HIV. In about 5% of infected individuals, HIV antibodies may take more than 6 months after exposure to reach detectable levels, but in most cases the antibodies are detectable in about 6 weeks. HIV testing may also be performed on oral fluid and urine samples. New rapid HIV tests can provide preliminary results in about 20 minutes.

The U.S. Food and Drug Administration has approved a number of drugs that may slow down the growth of HIV in the body and treat the infections and cancers associated with AIDS. The first group of drugs used to treat HIV, called nucleoside analog reverse transcriptase inhibitors (NRTIs), include the drug zidovudine (commonly known as AZT). Non-nucleoside reverse transcriptase inhibitors (NNRTIs) have also been approved to treat HIV. A third class of drugs, called protease inhibitors, are also approved for HIV. In 2003 the FDA granted accelerated approval of Fuzeon for use with other anti-HIV drugs to treat advanced cases of infection. Fuzeon was the first among a new class of medications called fusion inhibitors; drugs in this class interfered with HIV's entry into cells by hindering the fusion of viral and cellular membranes.

Patients are typically given a combination of different drugs, because HIV can much more easily become resistant to a single drug. While these drugs extend the period between HIV infection and serious illness, they do not prevent the spread of the disease to others, and can have severe side effects.

Since there is no vaccine or cure for AIDS, the only protection is to avoid activities that carry a risk. When it cannot be known with certainty whether a sexual partner has HIV, the CDC recommends abstinence (the only certain protection), mutual monogamy with an uninfected partner, or correct and consistent use of male latex condoms.

The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies.

Copyright Information: Public domain information with acknowledgement given to the U.S. National Library of Medicine.

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