Definition

Acquired immune deficiency syndrome (AIDS) is an infectious disease caused by the human immunodeficiency virus (HIV). There are two variants of the HIV virus, HIV-1 and HIV-2, both of which ultimately cause AIDS.

Description

AIDS was first recognized in the United States 1981 in homosexual men. Today is seen in both homosexual and heterosexual men and women. AIDS is the advanced form of infection with HIV virus. This virus may not cause recognizable symptoms for a long period after the initial exposure (latent period). As of early 2009, no vaccine was available to prevent HIV infection. Until such a vaccine is developed, all forms of HIV/AIDS therapy are focused on improving the quality and length of life for people who are infected by slowing or halting the replication of the virus and treating or preventing infections and cancers that often develop in people with AIDS.
AIDS is one of the most devastating worldwide public health problems in recent history. The United States Centers for Disease Control and Prevention (CDC) estimated that in 2006 944,000 people in the United States had been diagnosed with AIDS since the disease was identified in 1981. In 2006, an additional 1-1.2 million Americans were diagnosed as infected with HIV but not yet showing symptoms (HIV positive). However, in early 2009, the CDC issued a statement that they now thought that earlier the HIV-positive estimates were too low, as many more people than were originally estimated are living with unreported or undiagnosed HIV infection.
According to the August 2008 report issued by the Joint United Nations Programme on HIV/AIDS (UNAIDS), as of 2007, approximately 33 million people worldwide are HIV positive. Over half of the 33 million are women and this statistic has remained stable for several years. The highest number of cases is found in sub-Saharan Africa and Southeast Asia.
More than 70% of HIV infections are transmitted through sexual contact. Traditionally in the United States, the majority of cases were found in homosexual or bisexual men. In 2007, about half of new HIV cases were acquired by men having sex with other men. Fewer than 20% of HIV-positive Americans were women. However, this is not the case worldwide, where transmission by heterosexual individuals is common.
Risk of acquiring HIV infection by entry siteEntry siteRisk virus reaches entry siteRisk virus entersRisk inoculatedConjuntivaModerateModerateVery lowOral mucosaModerateModerateLowNasal mucosaLowLowVery lowLower respiratoryVery lowVery lowVery lowAnusVery highVery highVery highSkin, intactVery lowVery lowVery lowSkin, brokenLowHighHighSexual:VaginaPenisUlcers (STD)LowHighHighLowLowHighMediumLowVery highBlood:ProductsShared needles Accidental needleHighHighLowHighHighHighHigh Very High LowTraumatic woundModestHighHighPerinatalHighHighHigh

Risk factors

AIDS can be transmitted in several ways. The risk factors for HIV transmission vary according to the method of transmission.

• Sexual contact. People at greatest risk are those who do not practice safer sex by always using a condom, those who have multiple sexual partners, those who participate in anal intercourse, and those who have sex with a partner who has HIV infection and/or other sexually transmitted diseases (STDs). In the United States and Europe, most cases of sexually transmitted HIV infection result from homosexual contact, whereas in Africa, the disease is spread primarily through sexual intercourse among heterosexuals. Most people with AIDS in the United States are between 25 and 44 years of age.


• Transmission in pregnancy. High-risk mothers include women sexually active with bisexual men, intravenous drug users, and women living in neighborhoods with a high rate of HIV infection among heterosexuals. The chances of transmitting the disease to the child are higher in women in advanced stages of the disease. Breast feeding increases the risk of HIV transmission as HIV passes into breast milk. The rate of pediatric HIV transmission in the United States had decreased substantially because of HIV testing and improved drug treatment for infected mothers, so fewer than 1% of AIDS cases now occur in children under age 15. In the developing world, mother to infant transmission remains epidemic. In 2006, AIDS was the single most common cause of death in children under age 5 in South Africa, while worldwide children account for about 10% of all AIDS cases.


• Exposure to contaminated blood. Risk of HIV transmission among intravenous drug users increases with the frequency and duration of intravenous use, frequency of needle sharing, number of people sharing a needle, and the rate of HIV infection in the local population. In 2006, about 19% of men with AIDS and 25% of women with AIDS contracted the disease through sharing needles during intravenous drug injection. With the introduction of new blood product screening in the mid-1980s, HIV transmission through blood transfusions became rare in the developed world. However, contaminated blood is still a significant source of infection in the developing world.


• Needle sticks or body fluid splashes among health care professionals. Transmission through theses sources accounts for fewer than 0.3% of all HIV infections in the United States. This rate reflects the emphasis on universal safety precautions (e.g., use of gloves, face shields, proper disposal of needles) among health care professionals and first responders.

HIV is not transmitted by handshakes or other casual non-sexual contact, coughing or sneezing, or by bloodsucking insects such as mosquitoes.

AIDS in women

Women exposed to HIV infection through heterosexual contact are the most rapidly growing risk group in the United States. The percentage of AIDS cases diagnosed in American women has risen from 7% in 1985 to about 25% in 2006. According to the CDC, in 2006 approximately 278,400 women in the United States were living with HIV/AIDS. The rate was highest among black women and lowest among white women. About 75% of these women contracted HIV through high-risk heterosexual activity; almost all of the remainder acquired the infection through needle sharing.
The prevalence of women with HIV in the United States is low compared to the rate in many countries in the developing world. Worldwide about half the people living with HIV are women. According to the United Nations, in 2005 about 59% of women living in sub-Saharan Africa are infected with HIV. The vast majority of them were infected through sex with an infected male partner.

AIDS in children

Since AIDS can be transmitted from an infected mother to a fetus during pregnancy or to an infant during the birth process or through breastfeeding, all infants born to HIV-positive mothers are considered a high-risk group. However, prenatal drug treatment of HIV-positive mothers in developed countries has reduced the number of children born infected with HIV. In the developing world, drug treatment is either not available or not affordable. According to the United Nations Children's Fund (UNICEF) worldwide 2.3 million children under age 13 were living with HIV in 2006. The previous year, about 380,000 children died of AIDS and more than half a million children were newly infected. UNICEF estimates that at least 15 million children have lost at least one parent to AIDS.
AIDS is the leading causes of death in children under age five many parts of Africa and Southeast Asia. The interval between exposure to HIV and the development of AIDS is shorter in children than in adults. Infants infected with HIV have a high chance of developing AIDS within one year and dying before age three. In the remainder, AIDS progresses more slowly; the average child patient survives to about seven years of age. Some survive into early adolescence.

Causes and symptoms

AIDS is a disease that can damage any of the body's major organ systems because HIV destroys immune system cells. HIV attacks the body through three disease processes: immunodeficiency, autoimmunity, and nervous system dysfunction.
Immunodeficiency describes the condition in which the body's immune response is damaged, weakened, or is not functioning properly. In AIDS, immunodeficiency results from the way that the virus binds to a protein called CD4, which is primarily found on the surface of certain subtypes of white blood cells. After the virus has attached to the cell's CD4 receptor, the virus-CD4 complex refolds to uncover another receptor called a chemokine receptor that helps mediate entry of the virus into the cell. One chemokine receptor in particular, CCR5, has been the focus of recent research after studies showed that defects in its structure (caused by genetic mutations) result in a slowing or stopping of the progression of AIDS. Scientists hope that this discovery will lead to the development of drugs that trigger an artificial mutation of the CCR5 gene or target the CCR5 receptor.
Once HIV has entered the cell, it can replicate intracellularly and kill the cell in ways that are still not completely understood. In addition to killing some lymphocytes directly, the AIDS virus disrupts the functioning of the remaining immune system cells. Because the immune system cells are destroyed, a wide variety of infections and cancers can take advantage of a person's weakened immune system (opportunistic infections/diseases).
The course of AIDS generally progresses through three stages, although not all patients will follow this progression precisely:

Acute retroviral syndrome

Acute retroviral syndrome describes a group of symptoms that can resemble mononucleosis and that may be the first sign of HIV infection in 50-70% of all patients and 45-90% of women. Most patients are not recognized as HIV positive during this phase and may not seek medical attention. The symptoms are similar to those of many other diseases and may include fever, fatigue, muscle aches, loss of appetite, digestive disturbances, weight loss, skin rashes, headache, and chronically swollen lymph nodes (lymphadenopathy). Some patients will experience a form of meningitis during this phase in which the membranes that cover the brain and spinal cord become inflamed. Acute retroviral syndrome develops between one and six weeks after infection and lasts for two to three weeks. Blood tests during this period will indicate the presence of HIV virus (viremia) and the appearance of the viral p24 antigen in the blood.

Latency period

After the virus enters a person's lymph nodes during the acute retroviral syndrome stage, the disease becomes latent for 10 years or more before symptoms of advanced disease develop. During latency, the virus continues to replicate in the lymph nodes, where it may cause one or more of the following conditions:

Persistent generalized lymphadenopathy (PGL)

Persistent generalized lymphadenopathy, or PGL, is a condition in which HIV continues to produce chronic, painless swellings in the lymph nodes during the latent period. The lymph nodes that are most frequently affected by PGL are those in the areas of the neck, jaw, groin, and armpits. PGL affects between 50-70% of patients during latency.

Constitutional symptoms

Many patients develop low-grade fevers, chronic fatigue, and general weakness. HIV also may cause a combination of food malabsorption, loss of appetite, and increased metabolism that contribute to AIDS wasting syndrome.

Other organ systems

At any time during the course of HIV infection, patients may develop a yeast infection in the mouth called thrush, open sores or ulcers, or other infections of the mouth; diarrhea and other gastrointestinal symptoms that cause malnutrition and weight loss; diseases of the lungs and kidneys; and degeneration of the nerve fibers in the arms and legs. HIV infection of the nervous system leads to general loss of strength, loss of reflexes, and feelings of numbness or burning sensations in the feet or lower legs.

Late-stage disease (AIDS)

AIDS is usually marked by a very low number of CD4+ lymphocytes, followed by a rise in the frequency of opportunistic infections and cancers. Doctors monitor the number and proportion of CD4+ lymphocytes in the patient's blood in order to assess the progression of the disease and the effectiveness of different medications. About 10% of infected individuals never progress to this overt stage of the disease.

Opportunistic infections

Once the patient's CD4+ lymphocyte count falls below 200 cells/mm ³, he or she is at risk for a variety of opportunistic infections. The infectious organisms may include the following:

• Fungi. The most common fungal disease associated with AIDS is Pneumocystis carinii pneumonia (PCP). PCP is the immediate cause of death in 15-20% of AIDS patients. It is an important measure of a patient's prognosis. Other fungal infections include a yeast infection of the mouth (candidiasis or thrush) and cryptococcal meningitis.


• Protozoa. Toxoplasmosis is a common opportunistic infection in AIDS patients that is caused by a protozoan. Other diseases in this category include isoporiasis and cryptosporidiosis.


• Mycobacteria. AIDS patients may develop tuberculosis or mycobacterium avium complex (MAC) infections. MAC infections are caused by Mycobacterium avium-intracellulare and occur in about 40% of AIDS patients. This infection rarely develops until the CD4+ counts falls below 50 cells/mm³.


• Bacteria. AIDS patients are likely to develop bacterial infections of the skin and digestive tract.


• Viruses. AIDS patients are highly vulnerable to cytomegalovirus (CMV), herpes simplex virus (HSV), varicella zoster virus (VZV), and Epstein-Barr virus (EBV) infections. Another virus, JC virus, causes progressive destruction of brain tissue in the brain stem, cerebrum, and cerebellum (multifocal leukoencephalopathy or PML), which is regarded as an AIDS-defining illness by the CDC.

AIDS dementia complex and neurologic complications

AIDS dementia complex is usually a late complication of the disease. It is unclear whether it is caused by the direct effects of the virus on the brain or by intermediate causes. Loss of reasoning ability, loss of memory, inability to concentrate, apathy and loss of initiative, and unsteadiness or weakness in walking mark AIDS dementia complex. Some patients also develop seizures. There are no specific treatments for AIDS dementia complex.

Musculoskeletal complications

Patients in late-stage AIDS may develop inflammations of the muscles, particularly in the hip area, and may have arthritis-like pains in the joints.

Oral symptoms

In addition to thrush and painful ulcers in the mouth, patients may develop a condition called hairy leukoplakia. The CDC also regards this condition as an indicator of full-blown AIDS. Hairy leukoplakia is a white area of diseased tissue on the tongue that may be flat or slightly raised. It is associated with infection by the Epstein-Barr virus.

AIDS-related cancers

Patients with late-stage AIDS may develop Kaposi's sarcoma (KS), a skin tumor that primarily affects homosexual men. KS is the most common AIDS-related malignancy. It is characterized by reddish-purple blotches or patches (brownish in people with dark skin) on the skin or in the mouth. About 40% of patients with KS develop symptoms in the digestive tract or lungs. KS may be caused by a herpes virus-like sexually transmitted disease agent rather than HIV.
The second most common form of cancer in AIDS patients is a tumor of the lymphatic system (lymphoma). AIDS-related lymphomas often affect the central nervous system and develop very aggressively.
Invasive cancer of the cervix (related to certain types of human papilloma virus [HPV]) is an important diagnostic marker of AIDS in women.
While incidence of AIDS-defining cancers such as Kaposi's sarcoma and cervical cancer have decreased since increase use of antiretroviral therapy, other cancers have increased in AIDS patients. People with HIV have shown an increased incidence of lung cancer, head and neck cancers, Hodgkin's lymphoma, melanoma, and anorectal cancer.

Diagnosis

Because HIV infection produces a wide range of symptoms, the CDC has compiled a list of conditions regarded as defining AIDS. The physician will use the CDC list to decide whether the patient falls into one of these three groups:

• definitive diagnoses with or without laboratory evidence of HIV infection


• definitive diagnoses with laboratory evidence of HIV infection


• presumptive diagnoses with laboratory evidence of HIV infection.

Almost all the symptoms of AIDS can occur with other diseases. The general physical examination may range from normal findings to symptoms that are closely associated with AIDS. These symptoms are hairy leukoplakia of the tongue and Kaposi's sarcoma. During an examination, the doctor will look for an overall pattern of symptoms rather than any one definitive finding.

Laboratory tests for HIV infection

Blood tests (serology)

Diagnostic blood tests for AIDS are given to individuals in high-risk populations, pregnant women, health care and public service workers who have been exposed to HIV, those who have symptoms associated with AIDS, or others who fear they may have been exposed to the virus. The first blood test for AIDS was developed in 1985. Patients who are being tested for HIV infection are usually given an enzyme-linked immunosorbent assay (ELISA) test for the presence of HIV antibody in their blood. Positive ELISA results are then tested with a Western blot or immunofluorescence (IFA) assay for confirmation. The combination of the ELISA and Western blot tests is more than 99.9% accurate in detecting HIV infection within four to eight weeks following exposure. The polymerase chain reaction (PCR) test can be used to detect the presence of viral nucleic acids in the very small number of HIV patients who have false-negative results on the ELISA and Western blot tests. These tests are also used to detect viruses and bacteria other than HIV and AIDS.

Other laboratory tests

In addition to diagnostic blood tests, other blood tests are used to track the course of AIDS in patients that have already been diagnosed. These include blood counts, viral load tests, p24 antigen assays, and measurements of ₂-microglobulin (_2M).
Doctors will use a wide variety of tests to diagnose the presence of opportunistic infections, cancers, or other disease conditions in AIDS patients. Tissue biopsies, samples of cerebrospinal fluid, and sophisticated imaging techniques, such as magnetic resonance imaging (MRI) and computed tomography scans (CT) are used to diagnose AIDS-related cancers, some opportunistic infections, damage to the central nervous system, and wasting of the muscles. Urine and stool samples are used to diagnose infections caused by parasites. AIDS patients are also given blood tests for syphilis and other sexually transmitted diseases.

Diagnosis in children

The CDC recommends HIV testing as a part of standard prenatal care for all pregnant women. When a pregnant woman tests positive for HIV, testing of her infant ideally begins within 48 hours of birth. Testing is repeated at between 1 and 2 months of age and again at age 3-6 months. Testing of infants uses a different technique to detect the presence of HIV virus. Infants can be diagnosed by direct culture of the HIV virus, PCR testing, and p24 antigen testing. By one month of age, results are highly accurate. Diagnostic blood testing in children older than 18 months is similar to adult testing, with ELISA screening confirmed by Western blot.
In terms of symptoms, children are less likely than adults to have an early acute syndrome. They are, however, likely to have delayed growth, a history of frequent illness, recurrent ear infections, a low white blood cell count, failure to gain weight, and unexplained fevers. Children with AIDS are more likely to develop bacterial infections, inflammation of the lungs, and AIDS-related brain disorders than are HIV-positive adults.

Treatment

Drug treatment guidelines for HIV/AIDS change frequently as new drugs are approved and new drug regimens developed. Two principles currently guide doctors in developing drug regimens for AIDS patients: using combinations of drugs rather than one medication alone; and basing treatment decisions on the results of the patient's viral load tests. Current information on United States Food and Drug Administration-(FDA)approved drugs by class can be found at the United States Department of Health and Human Services Aids Info Website at . Individuals interested in participating in a trial of new HIV/AIDS drugs under development can find a list of clinical trials currently accepting volunteers at . There is not cost to volunteers to participate and some medical care and testing is provided.

Treatment of opportunistic infections and malignancies

Most AIDS patients require complex long-term treatment with medications for infectious diseases. This treatment is often complicated by the development of resistance in the disease organisms. AIDS-related malignancies in the central nervous system are usually treated with radiation therapy. Cancers elsewhere in the body are treated with chemotherapy.

Prophylactic treatment for opportunistic infections

Prophylactic treatment is treatment that is given to prevent disease. AIDS patients with a history of Pneumocystis pneumonia, with CD4+ counts below 200 cells/mm³ or 14% of lymphocytes, weight loss, or thrush should be given prophylactic medications. Drugs that may be given include antibiotics such as trimethoprim-sulfamethoxazole (Bactrim) or pentamidine (Pentam-300, Pentacarinat) and anti-fungals such as amphotericin B (AmBisome), flucytosine (Ancobon), and clotrimazole (Lotrim AF, Mycelex, Femizole-7). All these drugs can have undesirable side effects.

Anti-viral treatments

In recent years researchers have developed drugs that suppress HIV replication, as distinct from treating its effects on the body. These drugs fall into several classes:

• Nucleotide reverse transcriptase inhibitors (also called nucleoside analogues). These drugs work by interfering with the action of HIV reverse transcriptase inside infected cells, thus ending the virus's replication process. These drugs include zidovudine (Retrovir), lamivudine (Epivir), and abacavir (Ziagen) and many others. They are often used in used in multi-drug combinations.


• Non-nucleoside reverse transcriptase inhibitors. This class of drugs binds to an enzyme that is necessary for the HIV virus to reproduce. Examples of drugs in this class are viramune, delavirdine (Rescriptor), and efavirenz (Sustiva) and others.


• Protease inhibitors. Protease inhibitors work by disabling protease, an enzyme necessary for HIV reproduction. Protease inhibitors include saquinavir (Invirase), ritonavir (Norvire), indinavir (Crixivan), nelfinavir (Viracept), amprenavir (Agenerase), kaletra, and many others.


• Integrase inhibitors. Integrase inhibitors prevent the virus from inserting its own genetic material into the DNA of the infected cell. This stops the virus from replicating. Integrase was the only FDA-approved drug in this class as of early 2009. Several investigational drugs in this category were in clinical trials at that time.


• Fusion inhibitors and entry inhibitors. Fusion inhibitors block specific proteins on the surface of the virus or the CD4+ cell. These proteins help the virus gain entry into the cell. The only FDA-approved fusion inhibitor as of early 2009 was enfuvirtide (Fuzeon). Entry inhibitors block HIV from entering cells. The only FDA-approved fusion inhibitor as of early 2009 was maraviroc (Selzentry). Several drugs in this class are, as of 2009, in pre-approval clinical trials.

Stimulation of blood cell production

Because many patients with AIDS have abnormally low levels of both red and white blood cells, they may be given medications to stimulate blood cell production. Epoetin alfa (erythropoietin) may be given to anemic patients. Patients with low white blood cell counts may be given filgrastim or sargramostim.

Alternative treatment

Alternative treatments for AIDS can be grouped into two categories: those intended to help the immune system and those aimed at pain control. Treatments that may enhance the function of the immune system include Chinese herbal medicine and western herbal medicine, macrobiotic and other special diets, guided imagery and creative visualization, homeopathy, and vitamin therapy. Pain control therapies include hydrotherapy, reiki, acupuncture, meditation, chiropractic treatments, and therapeutic massage. Alternative therapies also can be used to help with side effects of the medications used in the treatment of AIDS.

Prognosis

As of early 2009, there was no cure for AIDS and no vaccine to prevent infection. Treatment stresses aggressive combination drug therapy for those patients with access to the expensive medications and who tolerate them adequately. The use of these multi-drug therapies has significantly improved and prolonged the life of HIV/AIDS patients in the United States.
Researchers are actively working on producing preventative and therapeutic vaccines for HIV. Preventative vaccines immunize an individual against a disease, so that he or she does not become infected. A therapeutic vaccine, also called a treatment vaccine, does not keep someone from getting a disease the way a preventative vaccine does. Instead, therapeutic vaccines are used to boost the body's immune system in order to help control infection. The potential exists to prolong life indefinitely using these and other drug therapies to boost the immune system, keep the virus from replicating, and ward off opportunistic infections and malignancies.

Prevention

As there is no cure for AIDS, prevention of HIV infection becomes extremely important in controlling the disease. Efforts to prevent the spread of AIDS include:

• Restricting sexual activity to a single partner and practicing safer sex (i.e., always using a condom). Besides avoiding the risk of HIV infection, condoms are successful in reducing other sexually transmitted diseases and unwanted pregnancies. Before engaging in a sexual relationship with someone, getting tested for HIV infection is recommended.


• Avoiding needle sharing among intravenous drug users.


• Donating one's own blood before planned major surgery to prevent risk of infection from a blood transfusion, although blood supplies are extremely safe in the developed world.


• Practicing universal safety precautions when handling body fluids or needles. Healthcare professionals, first responders, and teachers, for example, are now trained in these precautions.


• Testing for HIV infection by anyone how suspects infection. If treated aggressively and early, the development of AIDS may be postponed. If HIV infection is confirmed, it is also vital to let past sexual partners know so that they can be tested and receive medical attention.

Key Terms

Acute retroviral syndrome

A group of symptoms resembling mononucleosis that often are the first sign of HIV infection.

AIDS dementia complex

A type of brain dysfunction caused by HIV infection that causes difficulty thinking, confusion, and loss of muscular coordination.

Antibody

A protein produced by the immune system in response to a foreign protein or toxin called an antigen. Each different antigen stimulates the production of a different antibody.

Antigen

Any substance that stimulates the body to produce antibody.

Autoimmunity

A condition in which the body's immune system produces antibodies in response to its own tissues or blood components instead of foreign particles or microorganisms.

CCR5

A chemokine receptor; defects in its structure caused by genetic mutation cause the progression of AIDS to be prevented or slowed.

CD4

A type of protein molecule in human blood, sometimes called the T4 antigen, that is present on the surface of 65% of immune cells. The HIV virus infects cells with CD4 surface proteins, and as a result, depletes the number of immune system cells (T cells, B cells, natural killer cells, monocytes) in the individual's blood. Most of the damage to an AIDS patient's immune system is done by the virus' destruction of CD4+ lymphocytes.

Chemokine receptor

A receptor on the surface of some types of immune cells that helps to mediate entry of HIV into the cell.

Hairy leukoplakia of the tongue

A white area of diseased tissue on the tongue that may be flat or slightly raised. It is caused by the Epstein-Barr virus and is an important diagnostic sign of AIDS.

Hemophilia

Any of several hereditary blood coagulation disorders occurring almost exclusively in males. Because blood does not clot properly, even minor injuries can cause significant blood loss that may require a blood transfusion, with its associated minor risk of infection.

Human immunodeficiency virus (HIV)

A transmissible retrovirus that causes AIDS in humans. Two forms of HIV are now recognized: HIV-1, which causes most cases of AIDS in Europe, North and South America, and most parts of Africa; and HIV-2, which is chiefly found in West African patients. HIV-2, discovered in 1986, appears to be less virulent than HIV-1 and may also have a longer latency period.

Immunodeficient

A condition in which the body's immune response is damaged, weakened, or is not functioning properly.

Kaposi's sarcoma

A cancer of the connective tissue that produces painless purplish red (in people with light skin) or brown (in people with dark skin) blotches on the skin. It is a major diagnostic marker of AIDS.

Latent period

Also called incubation period, the time between infection with a disease-causing agent and the development of disease.

Lymphocyte

A type of white blood cell that is important in the formation of antibodies and that can be used to monitor the health of AIDS patients.

Lymphoma

A cancerous tumor in the lymphatic system that is associated with a poor prognosis in AIDS patients.

Macrophage

A large white blood cell, found primarily in the bloodstream and connective tissue, that helps the body fight off infections by ingesting the disease-causing organism. HIV can infect and kill macrophages.

Monocyte

A large white blood cell that is formed in the bone marrow and spleen. About 4% of the white blood cells in normal adults are monocytes.

(MAC) infection

A type of opportunistic infection that occurs in about 40% of AIDS patients and is regarded as an AIDS-defining disease.

Non-nucleoside reverse transcriptase inhibitors

The newest class of antiretroviral drugs that work by inhibiting the reverse transcriptase enzyme necessary for HIV replication.

Nucleoside analogues

The first group of effective anti-retroviral medications. They work by interfering with the AIDS virus' synthesis of DNA.

Opportunistic infection

An infection by organisms that usually do not cause infection in people whose immune systems are working normally.

Persistent generalized lymphadenopathy (PGL)

A condition in which HIV continues to produce chronic painless swellings in the lymph nodes during the latency period.

pneumonia (PCP)

An opportunistic infection caused by a fungus that is a major cause of death in patients with late-stage AIDS.

Progressive multifocal leukoencephalopathy (PML)

A disease caused by a virus that destroys white matter in localized areas of the brain. It is regarded as an AIDS-defining illness.

Protease inhibitors

The second major category of drug used to treat AIDS that works by suppressing the replication of the HIV virus.

Protozoan

A single-celled, usually microscopic organism that is eukaryotic and, therefore, different from bacteria (prokaryotic).

Retrovirus

A virus that contains a unique enzyme called reverse transcriptase that allows it to replicate within new host cells.

T cells

Lymphocytes that originate in the thymus gland. T cells regulate the immune system's response to infections, including HIV. CD4 lymphocytes are a subset of T lymphocytes.

Thrush

A yeast infection of the mouth characterized by white patches on the inside of the mouth and cheeks.

Viremia

The measurable presence of virus in the bloodstream that is a characteristic of acute retroviral syndrome.

Wasting syndrome

A progressive loss of weight and muscle tissue caused by the AIDS virus.

For Your Information

Resources

Books

• Silverstein, Alvin and Virginia Silverstein, and Laura Silverstein Nunn. The AIDS Update. Berkeley Heights, NJ: Enslow, 2008.

Organizations

• Gay Men's Health Crisis, Inc., 129 West 20th Street, New York, NY 10011-0022. (212) 807-6655.

Websites

• "Aids." MedlinePlus. January 9, 2009 [cited January 13, 2009]. http://www.nlm.nih.gov/medlineplus/aids.html.


• "AIDS Info." National Institutes of Health. January 9, 2009 [cited January 13, 2009]. http://www.aidsinfo.nih.gov .


• "U.S. National AIDS Hotlines & Resources." The Body.com. undated [cited January 13, 2009]. http://www.thebody.com/index/hotlines/national.html.

Other

• GHMC Web Peer Counseling. hotline@gmhc.org

Citations

For Gale Encyclopedia of Medicine:

AIDS. (n.d.) Gale Encyclopedia of Medicine. (2008). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For Dorland's Medical Dictionary:

AIDS. (n.d.) Dorland's Medical Dictionary for Health Consumers. (2007). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For The American Heritage® Medical Dictionary:

AIDS. (n.d.) The American Heritage® Medical Dictionary. (2007). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For Mosby's Medical Dictionary:

AIDS. (n.d.) Mosby's Medical Dictionary, 8th edition. (2009). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For Dictionary of Complementary and Alternative Medicine:

AIDS. (n.d.) Jonas: Mosby's Dictionary of Complementary and Alternative Medicine. (2005). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For Dental Dictionary:

AIDS. (n.d.) Mosby's Dental Dictionary, 2nd edition. (2008). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For Veterinary Dictionary:

AIDS. (n.d.) Saunders Comprehensive Veterinary Dictionary, 3 ed.. (2007). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS

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For McGraw-Hill Concise Dictionary of Modern Medicine:

AIDS. (n.d.) McGraw-Hill Concise Dictionary of Modern Medicine. (2002). Retrieved October 14 2012 from http://medical-dictionary.thefreedictionary.com/AIDS