Acquired Immune Deficiency Syndrome (AIDS): The most severe manifestation of infection with the Human Immunodeficiency Virus (HIV). The Centers for Disease Control and Prevention (CDC) lists numerous opportunistic infections and neoplasms (cancers) that, in the presence of HIV infection, constitute an AIDS diagnosis. In 1993, CDC expanded the criteria for an AIDS diagnosis to include CD4+ T-cell count at or below 200 cells per microliter in the presence of HIV infection. In persons (age 5 and older) with normally functioning immune systems, CD4+ T-cell counts usually range from 500-1,500 cells per microliter.

Antiretroviral (ARV): a substance that stops or suppresses the activity of a retrovirus, such as HIV.

AZT: A nucleoside reverse transcriptase inhibitor first approved by the FDA in 1987 and used in combination with other antiretroviral agents for the treatment of HIV infection in adults (ages 12+) and children 3 months to 12 years of age. In 1994, the FDA approved AZT for use in HIV-infected pregnant women beginning between 14 and 34 weeks gestation and during labor, and for use in newborn babies of HIV-infected mothers. Also known by the names Retrovir ® and Zidovudine.

CD4 (T) Cells: A type of T cell involved in protecting against viral, fungal, and protozoal infections. These cells normally orchestrate the immune response, signaling other cells in the immune system to perform their special functions. Also known as T helper cells. HIV's preferred targets. Destruction of CD4+ cells is the major cause of the immunodeficiency observed in AIDS. Lab work is done at specific intervals to measure the number of CD4 cells in circulation.

Deoxyribonucleic Acid (DNA): a double-stranded molecule that makes up the CHROMOSOMES in the center of a cell and that carries genetic information in the form of GENES. The genetic code utilized by DNA resides in the varying sequences of the four NUCLEOTIDE bases: ADENINE, GUANINE, THYMINE and CYTOSINE.

Drug Resistance: The ability of some disease-causing microorganisms, such as bacteria, viruses, and mycoplasma, to adapt themselves, to grow, and to multiply even in the presence of drugs that usually kill them. HIV often becomes resistant to antiretroviral therapies, necessitating a change in drug regimens.

Epidemic: A disease that spreads rapidly through a demographic segment of the human population, such as everyone in a given geographic area or everyone of a certain age or sex, such as the children or women of a region. Epidemic diseases can be spread from person to person or from a contaminated source such as food or water.

Hemophilia: A hereditary blood defect that occurs almost exclusively in males and is characterized by delayed clotting of the blood. This leads to difficulty in controlling bleeding, even after minor injuries. Ryan White was a hemophiliac.

Highly Active Antiretroviral Therapy (HAART):The name given to treatment regimens recommended by leading HIV experts to aggressively suppress viral replication and progress of HIV disease. The usual HAART regimen combines three or more different drugs such as two nucleoside reverse transcriptase inhibitors (NRTIs) and a protease inhibitor , two NRTIs and a non-nucleoside reverse transcriptase inhibitor (NNRTI) or other combinations. These treatment regimens have been shown to reduce the amount of virus so that it becomes undetectable in a patient's blood.

Hepatitis: An inflammation of the liver. May be caused by bacterial or viral infection, parasitic infestation, alcohol, drugs, toxins, or transfusion of incompatible blood. Although many cases of hepatitis are not a serious threat to health, the disease can become chronic and can sometimes lead to liver failure and death. There are three major types of viral hepatitis:

a). hepatitis A, caused by infection with the hepatitis A virus, which is spread by fecal-oral contact;

b). hepatitis B, caused by infection with the hepatitis B virus (HBV), which is most commonly passed on to a partner during intercourse, especially during anal sex, as well as through sharing of drug needles;

c). hepatitis c, caused by the hepatitis C virus, which appears to be spread through sexual contact as well as through sharing of drug needles (another type of non-A, non-B hepatitis is caused by the hepatitis E virus, principally spread through contaminated water);

Human Immunodeficiency Virus (HIV):The retrovirus isolated and recognized as the etiologic (i.e., causing or contributing to the cause of a disease) agent of AIDS.

HIV-2: A virus closely related to HIV-1 (the more common of the two across the globe, including all cases contracted in the U.S.) that also causes immune suppression and AIDS. The two viruses are very similar, but immunodeficiency seems to develop more slowly and to be milder in people infected with HIV-2. The majority of HIV-2 cases have been found in West Africa. Not all drugs used to treat HIV-1 infection are effective against HIV-2.

Immunodeficiency: a less than adequate functioning of the immune system (i.e. the inability to fight off illness and disease that an otherwise healthy immune system would be able to).

Kaposi's Sarcoma: An AIDS-defining illness caused by the HHV-8 virus, consisting of individual cancerous lesions caused by an overgrowth of blood vessels. KS typically appears as pink or purple painless spots or nodules on the surface of the skin or oral cavity. KS also can occur internally, especially in the intestines, lymph nodes, and lungs, and in this case is life threatening. The cancer may spread and also attack the eyes.

Opportunistic Infections:Illnesses caused by various organisms, some of which usually do not cause disease in persons with normal immune systems. Persons living with advanced HIV infection suffer opportunistic infections of the lungs, brain, eyes, and other organs. Opportunistic infections common in persons diagnosed with AIDS include Pneumocystis carinii pneumonia ; Kaposi's Sarcoma ; cryptosporidiosis ; histoplasmosis ; other parasitic, viral, and fungal infections; and some types of cancers.

Pandemic:essentially a large epidemic that crosses boundaries and affects many different subgroups within the larger population. Originally and falsely thought to be a "gay epidemic," HIV and AIDS is a global pandemic that requires everyone's attention.

Pneumocystis carinii pneumonia (PCP): An infection of the lungs caused by Pneumocystis carinii, which is thought to be a protozoa but may be more closely related to a fungus. P. carinii grows rapidly in the lungs of persons with AIDS and is a frequent AIDS- related cause of death. P. carinii infection sometimes may occur elsewhere in the body (skin, eye, spleen, liver, or heart). The standard treatment for persons with PCP is either a combination of trimethoprim and sulfamethoxazole (TMP/SMX, also called Bactrim or Septra), dapsone, or pentamidine.

Retrovirus: a type of virus that, when not infecting a cell, stores its genetic information on a single-stranded RNA molecule instead of the more usual double-stranded DNA. HIV is an example of a retrovirus. After a retrovirus penetrates a cell, it constructs a DNA version of its genes using a special enzyme, reverse transcriptase. This DNA can then become incorporated into the cell's genetic material.

Ribonucleic Acid (RNA): a single-stranded molecule composed of NUCLEOTIDE sequences. It is similar in basic structure to half of the double-stranded DNA. In cells, RNA transmits the code from the DNA-based GENES and instructs the cells' chemical machinery to produce structural PROTEINS and ENZYMES. The RNA segments in the cells represent copies of portions of the DNA sequences in the nucleus. In RETROVIRUSES, RNA is the sole repository of the viral genes.

Ryan White Care Act: The Ryan White Comprehensive AIDS Resources Emergency (CARE) Act is Federal legislation that addresses unmet health needs of people living with HIV (PLWH) by funding primary health care and support services. The legislation is named after the late Ryan White, and Indiana teenager whose courageous struggle with HIV & AIDS and related discrimination helped educate the nation. The CARE Act is administered by the Health Resources and Services Administration (HRSA).

Superinfection: A new infection acquired on top of an existing infection. For example, a person infected with one strain of HIV-1 can, if exposed to a different strain, become infected with the new strain in addition to the existing strain. Superinfection can complicate HIV treatment by requiring additional drugs to target the newly introduced HIV strain.

Sources and Additional Resources:

About.com - 2005
HIV/AIDS Glossary

Gay Men's Health Crisis - 2003
AIDS Medical Glossary and Drug Chart

U.S Department of Health and Human Services - 2006
AIDSinfo Glossary