Cachexia
Loss of weight, muscle wasting, fatigue, weakness, and decrease of appetite in someone who is not actively trying to lose weight. Usually associated with serious disease.

Candidiasis
Infection caused by a species of the yeast-like fungus Candida, usually C. albicans. Candidiasis can affect the skin, nails, and mucous membranes throughout the body, including the mouth (thrush), esophagus, vagina, intestines, and lungs. The infection appears as white patches when in the mouth or any other mucous membrane. Candidiasis is considered an AIDS-defining condition in people with HIV.

CAM
See: Complementary and Alternative Medicine

CARE Act
See:    Ryan White Care Act

Cardiomyopathy
A condition that weakens the heart muscle or causes a change in heart muscle structure. Cardiomyopathy is associated with inadequate heart pumping or other heart function abnormalities. Cardiomyopathy may occur in HIV-infected people with advanced disease. Irregular heartbeat, abnormal heart and breath sounds, decreased heart function, or heart enlargement may indicate cardiomyopathy.

CBC
See: Complete Blood Count

CBO
See: Community-Based Organization

CCR5
Chemokine receptor 5 (CCR5) is a protein on the surface of some immune system cells. It is one of two co-receptors that HIV can use along with the CD4 receptor to bind to and enter host cells (the other co-receptor is CXCR4).
See Also:   Co-Receptor
                   CXCR4
                   CD4 Receptor

CD4 Cell
Also known as helper T cell or CD4 lymphocyte. A type of infection-fighting white blood cell that carries the CD4 receptor on its surface. CD4 cells coordinate the immune response, signaling other cells in the immune system to perform their special functions. The number of CD4 cells in a sample of blood is an indicator of the health of the immune system. HIV infects and kills CD4 cells, leading to a weakened immune system.
See Also:   CD4 Cell Count
                   CD4 Receptor

CD4 Cell Count
A measurement of the number of CD4 cells in a sample of blood. The CD4 count is one of the most useful indicators of the health of the immune system and the progression of HIV/AIDS. A CD4 cell count is used by health care providers to determine when to begin, interrupt, or halt anti-HIV therapy; when to give preventive treatment for opportunistic infections; and to measure response to treatment. A normal CD4 cell count is between 500 and 1,400 cells/mm3 of blood, but an individual's CD4 count can vary. In HIV-infected individuals, a CD4 count at or below 200 cells/mm3 is considered an AIDS-defining condition.
See Also:   CD4 Cell

CD4 Percentage
The percent of lymphocytes (white blood cells) that are CD4 cells. This measurement is less likely to vary in between blood tests than CD4 count, but CD4 count remains a more reliable measure of immune function than CD4 percentage for most people.
See Also:   CD4 Cell Count
                   CD4 Cell

CD4 Receptor
A specific molecule present on the surface of a CD4 cell. HIV recognizes and binds to a CD4 receptor and a co-receptor to gain entry into a host cell.
See Also:   CD4 Cell
                   Co-Receptor

CD8 Cell
Also called a cytotoxic T lymphocyte (CTL), killer T cell, or suppressor T cell. A type of white blood cell that is able to identify and kill cells infected with bacteria, viruses, or other foreign invaders.

CDC
See: Centers For Disease Control and Prevention

CDCINFO
A service sponsored by the Centers for Disease Control and Prevention (CDC) to provide referrals, education, and information about topics including HIV/AIDS, other sexually transmitted diseases (STDs), immunizations, and disease outbreaks. The CDCINFO hotline number is 1-800-CDCINFO (232-4636).

Cell-Mediated Immunity
Immune protection provided by the direct action of immune cells. With this type of immune protection, the response to infectious micro-organisms is performed by specific cells, such as CD8 cells, macrophages, and other white blood cells, rather than by antibodies. The main role of cell-mediated immunity is to fight viral infections.
See Also:   Macrophage
                   Antibody

Cellular Immunity
See:    Cell-Mediated Immunity

Centers For Disease Control and Prevention (CDC)
An agency of the U.S. Department of Health and Human Services (DHHS) that is charged with protecting the health and safety of citizens at home and abroad. The CDC serves as the national focus for developing and applying disease prevention and control, environmental health, and health promotion and education activities designed to improve the health of the people of the United States.

Centers for Medicare and Medicaid Services (CMS)
Previously known as the Health Care Financing Administration (HCFA). An agency of the U.S. Department of Health and Human Services (DHHS) responsible for administering Medicare, Medicaid, State Children's Health Insurance Program (SCHIP), Health Insurance Portability and Accountability Act (HIPAA), Clinical Laboratory Improvement Amendments (CLIA), and other health-related programs.

Central Nervous System (CNS)
The part of the nervous system made up of the brain, spinal cord, and spinal nerves. These serve as the main "processing center" for the whole nervous system, and together control all the workings of the body. HIV can infect and damage parts of the central nervous system.

Cerebrospinal Fluid (CSF)
A clear, colorless fluid that fills the spaces in the brain and the central canal of the spinal cord, as well as the spaces between nerve cells.

Cervical Cancer
A condition in which a cancerous growth (also called a malignancy) develops on the lower portion of the uterus (cervix).
See Also:   Cervical Dysplasia
                   Pap Smear
                   Human Papillomavirus

Cervical Dysplasia
The abnormal growth of cervical cells, usually with no symptoms. It can be detected by a Pap smear and treatment can prevent it from progressing to cervical cancer.
See Also:   Cervical Cancer
                   Pap Smear
                   Human Papillomavirus

Cervical Intraepithelial Neoplasia (CIN)
A general term for the growth of abnormal cells on the surface of the cervix. Numbers from 1 to 3 may be used to describe how much of the cervix contains abnormal cells.
See Also:   Cervical Dysplasia

Cervix
The lower, narrow end of the uterus that forms a canal between the uterus and vagina.

Chancroid
A sexually transmitted disease (STD) caused by a bacterium called Hemophilus ducreyi. Often causes swollen lymph nodes and painful sores on the penis, vagina, or anus. The lesions appear after an incubation period of 3 to 5 days and may facilitate HIV transmission.

Chemokines
Proteins that serve as chemical messengers to control the activities of the immune system. Chemokines are involved in a wide variety of processes, including the control of infectious diseases, cancers, and inflammation. Chemokines include interferons, interleukins, and many other small proteins.

Chemotherapy
Treatment using anti-cancer drugs, which kill or prevent the growth and division of cells. The drugs enter the bloodstream and travel through the body killing mostly cancer cells, but also some healthy cells.

Chlamydia
A sexually transmitted disease (STD) caused by a bacterium called Chlamydia trachomatis. The bacteria infect the genital tract and if left untreated can cause damage to the female and male reproductive systems, resulting in infertility.

Cholesterol
A fat-like substance used as a building block for cells. Cholesterol is both made by the liver and absorbed from food and is carried in the blood. When blood cholesterol levels are too high (hyperlipidemia), some of the cholesterol is deposited on the walls of the blood vessels, increasing the risk of heart disease and atherosclerosis. Use of PIs may also increase cholesterol levels.
See Also:   Hyperlipidemia

Chronic Idiopathic Demyelinating Polyneuropathy (CIPD)
Chronic, spontaneous loss or destruction of myelin, a white fatty material that protects and insulates nerve cells. People with CIPD show progressive, usually symmetrical weakness in the arms and legs. CIPD can be one of the symptoms of lactic acidosis or progressive multifocal leukoencephalopathy.
See Also:   Lactic Acidosis
                   Progressive Multifocal Leukoencephalopathy

CIN
See: Cervical Intraepithelial Neoplasia

CIPD
See: Chronic Idiopathic Demyelinating Polyneuropathy

CIPRA
See: Comprehensive International Program of Research on AIDS

Clade
A group of organisms that are genetically similar and descended from a single parent organism. With HIV, the term "clade" refers to a group of specific HIV-1 strains within an HIV subtype. For example, HIV-1 subtype M contains clades A through H, J, and K. Clades B and C account for the majority of HIV infections around the world.
See Also:   Subtype

Class-Sparing Regimen
An anti-HIV drug regimen that purposefully does not include one or more classes of anti-HIV drugs. A class-sparing regimen may be prescribed to "save" certain classes of drugs for later use or to avoid side effects specific to a class. For example, a PI-sparing regimen would not include any PIs. Because some PIs may cause an increase in cholesterol in the blood, a PI-sparing regimen might be prescribed for an HIV-infected person who already has high cholesterol levels.

Clinical Alert
The National Institutes of Health (NIH) publishes these electronic bulletins containing urgent early results of clinical trials. The data in these bulletins warn about possible morbidity (sickness rates) and mortality (death rates) in participants involved in the clinical trials.

Clinical Endpoint
A measurement used in clinical trials to evaluate the effect of the treatment being tested. Examples of clinical endpoints for HIV disease include death, serious drug toxicity, or development of an AIDS-defining illness. Because these endpoints may be difficult to measure without long-term follow-up, surrogate (substitute) short-term endpoints, such as a change in viral load or CD4 count, may also be used as clinical endpoints.
See Also:   Clinical Trial

Clinical Failure
The occurrence or recurrence of HIV-related infections or a decline in physical health despite taking an HIV treatment regimen for a minimum of three months. Clinical failure may occur as a result of virologic or immunologic failure.
See Also:   Virologic Failure
                   Immunologic Failure

Clinical Practice Guidelines
Recommendations by panels of expert health care practitioners designed to assist clinicians and patients in making decisions about appropriate health care for specific diseases and conditions.

Clinical Trial
A research study that uses human volunteers to answer specific health questions. Carefully conducted clinical trials are regarded as the fastest and safest way to find effective treatments for diseases and conditions, as well as other ways to improve health. Interventional trials use controlled conditions to determine whether experimental treatments or new ways of using known treatments are safe and effective. Observational trials gather information about health issues from groups of people in their natural settings.

ClinicalTrials.gov
An online, searchable database of information about clinical trials sponsored by governments, pharmaceutical companies, and other organizations. This database is managed by the National Institutes of Health (NIH) through its National Library of Medicine (NLM). The Web address for the database is www.clinicaltrials.gov
See Also:   Clinical Trial

CMAX
The maximum (peak) amount of drug measurable in the blood after a dose is administered.
See Also:   CMIN

CMIN
The lowest (trough) amount of drug measurable in the blood after a dose is administered.
See Also:   CMAX

CMS
See: Centers for Medicare and Medicaid Services

CMV
See: Cytomegalovirus

CMV Retinitis
See:    Cytomegalovirus Retinitis

CNS
See: Central Nervous System

Coccidioidomycosis
Also called desert fever, San Joaquin Valley fever, or valley fever. An infectious disease caused by the inhalation of spores of Coccidioides immitis. The disease is especially common in hot, dry regions of the Southwestern United States and Central and South America. It is an AIDS-defining condition in people with HIV.
See Also:   AIDS-Defining Condition

Cognitive Impairment
Loss of the ability to process, learn, and remember information. The progression of HIV disease may lead to cognitive impairment.
See Also:   HIV-Associated Dementia

Cohort
A group of individuals who are alike in some way. For example, the people in a cohort of HIV-infected individuals are all infected with HIV.

Co-Infection
Infection with more than one virus, bacterium, or other micro-organism at a given time. For example, an HIV-infected individual may be co-infected with hepatitis C virus (HCV) or tuberculosis (TB).

Colitis
Inflammation of the colon (large intestine). This may lead to intestinal bleeding, ulcers, or perforations (holes) in the colon.

Combination Therapy
Two or more drugs used together to achieve optimal results in controlling HIV infection. Combination therapy has proven more effective in decreasing viral load than monotherapy (single-drug therapy), which is no longer recommended for the treatment of HIV. An example of combination therapy is the use of two NRTIs plus a PI or an NNRTI.

Community-Based Organization (CBO)
A service organization that provides social services to local clients. CBOs include nonprofit organizations and free clinics targeted at helping people with HIV.

Community Programs for Clinical Research on AIDS (CPCRA)
Also known as the Terry Beirn Community Programs for Clinical Research on AIDS. A network of clinical research units composed of community-based health care providers. CPCRA's aim is to serve populations under-represented in previous clinical trials. CPCRA is funded by the National Institute of Allergy and Infectious Diseases (NIAID).

Co-Morbid Condition
Any disease or condition that occurs at the same time as another disease or condition. The second disease may worsen or be worsened by the initial disease. For example, tubuculosis (TB) may occur as a co-morbid conditon in an individual infected with HIV, and the HIV infection may worsen the TB.

Compassionate Use
General term used to describe any program that provides an experimental therapy outside of clinical trials to patients who do not have any FDA-approved treatment options (for example, HIV-infected individuals who have extensive drug resistance to approved anti-HIV drugs). To enroll in compassionate use programs, an individual has to meet strict medical critera.
See Also:   Expanded Access
                   Investigational Drug

Complementary and Alternative Medicine (CAM)
Health care practices not currently considered part of conventional medicine. A therapy is called complementary when it is used in addition to conventional treatments. It is called alternative when it is used instead of conventional treatment. CAM includes a broad range of healing therapies, approaches, and systems. Some examples of CAM are acupuncture, herbs, homeopathy, chiropractic, hypnosis, and traditional Chinese medicine.

Complete Blood Count (CBC)
A general blood test that measures the levels of white and red blood cells, platelets, hematocrit, and hemoglobin in a sample of blood. Changes in the amounts of each of these may indicate infection, anemia, or other health problems.

Comprehensive International Program of Research on AIDS (CIPRA)
A program administered by the National Institute of Allergy and Infectious Diseases (NIAID) to support research and development of practical, affordable, and acceptable methods to prevent and treat HIV/AIDS in resource-poor countries.

Condyloma Acuminatum
See:    Genital Warts

Contagious
Easily passable between people through normal day-to-day contact. For example, chicken pox is both an infectious (causing infection) and a contagious disease. In contrast, HIV is an example of an infectious disease that is not a contagious disease (it cannot be passed from person to person through casual contact).

Contraindication
A specific situation in which a particular treatment should NOT be used because it may be harmful to the patient. For example, some anti-HIV drugs are primarily broken down by the liver, and should not be given to people who have liver damage.

Controlled Trial
A control is a standard against which experimental treatments may be compared and evaluated for safety and effectiveness. In clinical trials, one group of patients may be given an experimental drug, while another group (the control group) is given either a standard treatment for the disease or a placebo.
See Also:   Placebo

Core
The inner protective coat of protein that surrounds the genetic material of most viruses. In HIV, the core is mostly made up of the p24 protein, which surrounds two copies of HIV's genetic material.

Co-Receptor
A protein on the surface of a cell that serves as a second binding site for a virus or other molecule. Although the CD4 protein is HIV's primary receptor, the virus must also bind either the CCR5 or CXCR4 co-receptor to get into a host cell.
See Also:   CCR5
                   CXCR4
                   CD4 Receptor

CPCRA
See: Community Programs for Clinical Research on AIDS

Creatinine
A protein found in muscles and blood and excreted by the kidneys into the urine. The level of creatinine in the blood or urine provides a measure of kidney function. Increased levels of creatinine indicate abnormal or impaired kidney function.

Cross Resistance
Cross resistance occurs when a micro-organism has changed (mutated) in such a way that it loses its susceptibility to multiple drugs simultaneously. For example, HIV resistance to one NNRTI drug usually produces resistance to the entire NNRTI drug class.
See Also:   Drug Resistance
                   Non-Nucleoside Reverse Transcriptase Inhibitors

Cross Sensitivity
Occurrence of a drug reaction that may occur again with the use of a different, but related, drug. Cross sensitivity can occur within a drug class, such as when a person reacts to all NNRTIs similarly after treatment with just one. Cross sensitivity can also occur among chemically similar drug classes. For example, a person who has a negative side effect to a sulfa-based antibiotic is at risk for the same negative side effect if he or she takes any other sulfa-based drug.

Cryotherapy
The use of liquid nitrogen to freeze and destroy a lesion or growth to prevent further spread of the growth. In people with HIV, it is used to treat lesions caused by Kaposi's sarcoma and condyloma acuminatum (genital warts).
See Also:   Genital Warts
                   Kaposi's Sarcoma

Cryptococcal Meningitis
A life-threatening infection of the membranes surrounding the brain and the spinal cord caused by the fungus Cryptococcus neoformans. Symptoms include headache, dizziness, stiff neck, and, if untreated, coma and death. Immunocompromised individuals are more susceptible to this infection. It is considered an AIDS-defining condition in people with HIV.

Cryptococcosis
An infection caused by the fungus Cryptococcus neoformans. This fungus typically enters the body through the lungs and usually spreads to the brain, causing cryptococcal meningitis. In some cases, it can also affect the skin, skeletal system, and urinary tract. It is considered an AIDS-defining condition in people with HIV.
See Also:   Cryptococcal Meningitis

Cryptosporidiosis
A diarrheal disease caused by the protozoa Cryptosporidium. Symptoms include abdominal cramps and severe chronic diarrhea. It is considered an AIDS-defining condition in people with HIV.
See Also:   Cryptosporidium

Cryptosporidium
The protozoan that causes cryptosporidiosis. It is found in the intestines of animals and may be transmitted to humans by direct contact with an infected animal, by eating contaminated food, or by drinking contaminated water.
See Also:   Cryptosporidiosis

CSF
See: Cerebrospinal Fluid

CTL
See: Cytotoxic T Lymphocyte

Cutaneous
Of, relating to, or affecting the skin.

CXCR4
Chemokine receptor 4 (CXCR4, also known as fusin) is a protein on the surface of some immune system cells. It is one of two co-receptors that HIV can use along with the CD4 receptor to bind to and enter host cells (the other co-receptor is CCR5).
See Also:   Co-Receptor
                   CD4 Receptor
                   CCR5

CYP450
See: Cytochrome P450

Cytochrome P450 (CYP450)
A system of enzymes, located primarily in the liver, that participate in the break-down of drugs. Many drugs inhibit or enhance the activity of these enzymes. Any change in CYP450 enzyme activity may cause an increase or decrease in blood levels of drugs broken down through this system.
See Also:   Drug Interaction

Cytokines
Proteins produced by white blood cells that act as chemical messengers between cells. Cytokines can stimulate or inhibit growth or activity of immune cells and are essential for a coordinated immune response. Cytokines include the interleukins and the interferons.

Cytomegalovirus (CMV)
A herpesvirus that can cause infections, including pneumonia (infection of the lungs), gastroenteritis (infection of the gastrointestinal tract), encephalitis (inflammation of the brain), or retinitis (infection of the eye), in immunosuppressed people. Although CMV can infect most organs of the body, HIV-infected people are most susceptible to CMV retinitis.
See Also:   Cytomegalovirus Retinitis
                   Herpesviruses

Cytomegalovirus Retinitis
An infectious eye disease caused by cytomegalovirus (CMV). People with CMV retinitis can lose their vision, and CMV retinitis is the most common cause of blindness among people infected with HIV.
See Also:   Cytomegalovirus

Cytopenia
A condition in which the production of one or more kind of blood cells is greatly reduced or stops completely. Some medications used to treat HIV or cancer may cause cytopenia.

Cytotoxic
Toxic or destructive to cells. For example, cancer chemotherapy is cytotoxic because it destroys both cancerous and noncancerous cells.

Cytotoxic T Lymphocyte (CTL)
See:    CD8 Cell