Acquired immunodeficiency syndrome (AIDS) is a fatal disease in which the immune system is weakened by the human immunodeficiency virus or HIV. It is often referred to as HIV/AIDS. A healthy immune system fights off infections andcertain diseases. HIV is a serious infection that progressively kills or impairs immune system cells. AIDS is not a single disease; it covers a wide rangeof symptoms and illnesses that can occur when the HIV virus becomes advancedenough to severely deplete the immune system. People who have AIDS can develop a variety of illnesses that are life-threatening.

AIDS was first recognized in the United States in 1981 and is now considereda worldwide epidemic. Anyone can get AIDS. In the United States, it is considered one of the most devastating public health problems in recent history. In1998, the Centers for Disease Control and Prevention (CDC) estimated that 650,000 to 950,000 Americans were living with HIV infection (this is called being HIV-positive). More than 200,000 of these people did not know that they were infected. Approximately 40,000 of them became infected that year; about 70percent were men, 30 percent were women, and half are 25 years of age or younger. Half of the people infected in 1998 were 25 years of age or younger. CDC also estimated that 297,137 people in the United States were living with AIDS in 1998; this was a 10% increase from the same figure for 1997. Through June 30, 1999, 711,344 cases of AIDS and 420,201 deaths among people with AIDSin the United States had been reported to the CDC. In the United States, AIDSis now the fifth leading cause of death among people aged 25 to 44. Worldwide, CDC estimated that at the end of 1998, 33.4 million people-32.2 million adults and 1.2 million children under the age of 15-were living with HIV/AIDS.Approximately one in every 100 people aged 15-49 are infected with HIV. During 1998, approximately 5.8 million people, primarily those living in developing countries, were infected with HIV. This means that approximately 16,000 people were infected every day. Through 1998, approximately 13.9 million people-10.7 million adults and 3.2 million children-have died of HIV/AIDS or associated conditions.

Most people who are infected with HIV have no symptoms and do not know that they have the virus. Once they are infected, however, they can infect other people. People can get HIV through sexual contact, direct contact with the blood of an infected person, mother to child, and blood transfusions. The virus is usually spread by sexual contact with an infected partner, through semen orvaginal fluids. Sexual conduct can be oral, anal, or vaginal between same- or opposite-sex partners. The most common form of direct blood contact is sharing needles, for example, among intravenous drug users tattooing, and piercing. A mother with HIV can spread the infection to her child during pregnancy,birth, or while breastfeeding. The risk of becoming infected through a bloodtransfusion is very low, since all blood and blood products are now tested for HIV antibodies. Health care professionals who work with body fluids can also become infected, although the risk is low (less than 0.3 percent). HIV is not spread by casual contact such as kissing, sharing objects in the house, public toilets, water fountains, swimming pools, or bugs.

HIV destroys white blood cells called CD4 (T cell lymphocytes that normally fight off attacks by bacteria, viruses, and other germs). Healthy people haveCD4 cell counts that range from 500 to 1800. CDC defines AIDS as being present in people who are infected with HIV whose CD4 count falls below 200. CDC also uses 26 clinical conditions that affect people with advanced HIV disease to define AIDS. People who are infected with HIV usually experience a gradualdecline in the number of CD4 cells, although in some people, this can happensuddenly. People with CD4 counts above 200 may have early symptoms of HIV disease, and people with CD4 counts below 200 may not have any symptoms.

HIV attacks the body through three disease processes: immunodeficiency, autoimmunity, and nervous system dysfunction. Immunodeficiency means that the immune system is weakened or does not work properly. Infections and cancers can take advantage of the situation and cause disease. Autoimmunity is a conditionin which the immune system works against the body's own cells. Researchers do not know precisely how HIV attacks the nervous system. One theory is that,once infected with HIV, one type of immune system cell, called a macrophage,releases a toxin that harms the nervous system.

Testing for HIV infection is done in most doctors' offices or health clinics.HIV infection is diagnosed through a blood test called the EHSA (enzyme-linked immunosorbent assay) which detects HIV antibodies. This can only be done 3to 6 months after suspected exposure to HIV, because it takes time for the body to develop HIV antibodies. If this test shows that the person is HIV-positive, an HIV RNA blood test can be done to measure the amount of HIV virus inhis/her blood. For most people with HIV infection, the time between exposureto the virus and the progression of AIDs is 10 to 12 years. Because HIV infection produces such a wide range of symptoms, doctors look for the overall pattern of symptoms. They ask about exposure to HIV-infected body fluids, checkfor HIV/AIDS signs and symptoms, and do a physical exam. These signs and symptoms include fever, weight loss, a thick white coating on the tongue, and Kaposi's sarcoma (a rare cancer in people with weak immune systems). To confirmthe diagnosis of AIDS in someone who is HIV-positive, a blood test for CD4 cell count is done; if the count is below 200, the person has AIDS. Doctors use other tests to diagnose conditions related to AIDS, like opportunistic infections, cancers, brain illness, tumor, body wasting, or lung illness.

HIV/AIDS and related illness are different for each person. The course of thedisease, however, generally progresses through three stages: acute retroviral syndrome, latency (when the disease is silent), and late-stage AIDS. The first stage of AIDS is usually acute retroviral syndrome. Possible warning signs of infection with HIV are: rapid weight loss; dry cough; fever or night sweats that happen again and again; lasting fatigue with no known cause; swollenlymph glands in the armpits, groin, or neck; diarrhea that lasts for more than a week; white spots or marks on the tongue, mouth, or throat; pneumonia; red, brown, or purplish blotches on or under the skin or inside the mouth, nose, or eyelids; and memory loss, depression, or other neurological disorders.Acute retroviral syndrome develops between one and six weeks after people become infected and lasts for two to three weeks. People with HIV are very infectious during this stage.

During the acute retroviral syndrome stage, the HIV virus enters the lymph nodes. The disease then enters the second stage and becomes latent (where thereare no signs or symptoms of it), often for many years. However, the virus continues to replicate in the lymph nodes. Many people who are infected with HIV experience chronic painless swellings in the lymph nodes. Other symptoms which may appear before the infection progresses to AIDS include: a lack of energy, weight loss, frequent fevers and sweats, yeast infections, skin rashes,pelvic inflammatory disease, and short-term memory loss. Some people with HIVinfection develop herpes infections or a painful nerve disease called shingles.

At any time during HIV infection, patients may suffer from a yeast infectionin the mouth called thrush or other mouth infections; diarrhea and other gastrointestinal symptoms; diseases of the lungs and kidneys; and degeneration ofnerve fibers in the arms and legs. HIV infection of the nervous system leadsto loss of strength and reflexes and feelings of numbness or burning in thefeet or lower legs.

Many people with HIV that has progressed to AIDS cannot work steadily or do chores around the house because the symptoms are so severe. Other people withAIDS may go through periods of life-threatening illness followed by normal functioning. AIDS is usually marked by a sharp decline in the number of CD4+ lymphocytes (a type of immune system cell), followed by a rise in infections and cancers. Once the patient's CD4+ lymphocyte count falls below 200 cells/mm3, the risk for opportunistic infections, which develop because theweakened immune system gives them the opportunity to develop, increases sharply. These infections rarely harm people with healthy immune systems but theycan be life-threatening and sometimes fatal to people with AIDS. AIDS patients easily develop bacterial infections and are highly vulnerable to viral infections. A common fungal disease associated with AIDS is Pneumocystis carinii pneumonia (PCP). Other fungal infections include candidiasis or thrush. Toxoplasmosis is caused by a protozoan, as are amebiasis and cryptosporidiosis. Cancers caused by AIDS such as Kaposi's sarcoma and cervical cancer, and cancers of the immune system (called lymphomas) are usually more severe andmore difficult to treat in people with AIDS than in other people. Opportunistic infections cause symptoms like coughing; shortness of breath; seizures; mental symptoms like confusion and forgetfulness; severe and ongoing diarrhea;fever; loss of vision; severe headaches; weight loss; extreme fatigue; nausea; vomiting; lack of coordination; coma; abdominal cramps; or difficult or painful swallowing. Children with AIDS may also get severe cases of childhood bacterial infections such as conjunctivitis (pink eye), ear infections, and tonsillitis.

AIDS dementia complex is a late complication. It is marked by loss of reasoning and memory, inability to concentrate, apathy, and unsteadiness or weaknessin walking. Some patients also develop seizures. There are no specific treatments for AIDS dementia complex. Patients in late-stage AIDS may develop inflammations of the muscles and may have arthritis-like pains in the joints.

Patients with late-stage AIDS may develop Kaposi's sarcoma, a type of skin tumor. It is the most common AIDS-related cancer. The second most common form of cancer in AIDS patients is a tumor of the lymphatic system (lymphoma).

There is no cure for AIDS, which is a lifelong illness. Thanks to new and effective treatments, however, people with HIV/AIDS are living longer, healthierlives. People with HIV/AIDS should go to a doctor who knows how to treat this disease. Antiretroviral drugs are used to fight HIV infection. A combination of these drugs is usually used to make treatment more effective and limit the risk of developing drug-resistant HIV. Three types of antiretroviral drugsare used: nucleoside analogues like zidovudine (Retrovir or AZT), protease inhibitors like saquinavir (Invirase and Fortovase), and non-nucleoside reverse transcriptase inhibitors like nevirapine (Viramune). Nucleoside analogues interrupt an early stage of virus replication and may slow the spread of HIV in the body and delay the start of opportunistic infections. They do not, however, prevent people with HIV from spreading the virus to others. Non-nucleoside reverse transcriptase inhibitors are used in combination with other antiretroviral drugs. Protease inhibitors interrupt virus replication at a later step in its life cycle. Highly Active Antriretroviral Therapy (HAART), a combination of three drugs (two nucleoside analogues and one protease inhibitor), is a common treatment for AIDS. These antiretroviral drugs all have side effects that can be severe, such as a depletion of red or white blood cells, especially during the later stages of the disease, an inflammation of the pancreas, and painful nerve damage. The most common side effects of protease inhibitors include nausea, diarrhea, and other gastrointestinal symptoms. They can also produce serious side effects through interactions with other drugs. More than 22 drugs are available to treat AIDS-related conditions such as opportunistic infections and Kaposi's sarcoma. People with CD4 counts below 200 are also given treatment to prevent Pneumocystic carinnin pneumonia, one of the most common and deadly opportunistic infections associated with HIV. AIDS-related malignancies in the central nervous system are usually treated with radiation therapy. Cancers elsewhere in the body are treated with chemotherapy.

There are also many things that people with HIV/AIDS can do live longer and healthier lives. They should follow their doctor's instructions, including keeping appointments and taking medicines exactly as prescribed; getting shots to prevent infections like pneumonia and flu; quit smoking or taking drugs that are not prescribed by a doctor; eat healthy; exercise; get enough sleep andrest; and relax through prayer, meditation, or other methods.

The risk of death for people with HIV that has progressed to AIDS varies tremendously. Some people die shortly after diagnosis, while others live 12 or more years. AIDS patients who are male, young adults, white, and have Kaposi'ssarcoma as the first sign of the illness usually live longer than others. Since the newer antiretroviral drugs were approved in 1995, the death rate and number of hospitalizations in the United States have both decreased.

Preventing HIV/AIDS is crucial, according to the CDC. During the 1980s, manyprevention efforts were begun; these have had a major impact on slowing the HIV/AIDS epidemic in the United States. People can decrease their chances of becoming infected with HIV by changing their behavior so that they:

  • Have sex with only one partner or use barrier methods of contraception, like condoms,
  • Donate their own blood before surgery for use during surgery, and
  • Do not share needles.

Health care workers should follow infection control procedures related to exposure to body fluids. Women who have a history of behaviors that put them atrisk for HIV and are thinking about becoming pregnant should have a test forHIV before becoming pregnant.

People who are infected with HIV can also protect other people from infectionby:

  • Not having sex is the best way to prevent spreading the disease,but people with HIV who have sex should use a latex condom. If a lubricant isused, choose one that is water-based. If spermicide is used, follow the instructions,
  • Using protection during oral sex, such as a condom or plastic food wrap,
  • Not sharing sex toys,
  • Not sharing drug needlesor drug works,
  • Telling people they have had sex with that they haveHIV,
  • Not donating blood, plasma, or organs, and
  • Not sharing razors or toothbrushes.

Women with HIV who take zidouvudine (AZT) during pregnancy significantly reduce the change of spreading the disease to their babies. Taking AZT and delivering the baby through a cesarean section can reduce the infection rate to onepercent.

No one knows where HIV came from. Scientists are continually doing more research to learn more about HIV and AIDS. Their discoveries help people learn howto stop the spread of the virus and how to help people who are infected withHIV live longer, healthier lives. Researchers supported by the National Institute of Allergy and Infectious Diseases are doing research on vaccines and new therapies for HIV and conditions associated with the infection. More thana dozen HIV vaccines are being tested in people, and many drugs for HIV infection or opportunistic infections associated with AIDS are either in development or being tested. Researchers are also trying to discover how HIV damages the immune system.

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