C
Physical wasting (loss of body weight and muscle mass) frequently associated with chronic disease, such as cancer or AIDS.
An enteric (intestinal) infection caused by the bacterium
Campylobacter. Symptoms of campylobacteriosis, if any, include diarrhea (often bloody), abdominal cramping and pain, nausea and vomiting, fever, and fatigue. Some people with campylobacteriosis may develop Guillain-Barré syndrome. Certain bacterial enteric infections, including campylobacteriosis, occur at a much higher rate in people with HIV than in the general population.
See Related Term(s): Guillain-Barré Syndrome
Also known as: Yeast Infection
A fungal infection caused by overgrowth of the yeast
Candida (usually
Candida albicans) in moist areas of the body. Candidiasis can affect the mucous membranes of the mouth, vagina, and anus. In people with HIV, candidiasis of the bronchi, trachea, lungs, or esophagus is an AIDS-defining condition.
See Related Term(s): AIDS-Defining Condition, Opportunistic Infection
Disease of the heart muscle. Cardiomyopathy weakens the heart muscle, making it hard for the heart to pump blood to the rest of the body. HIV infection or use of some antiretroviral (ARV) drugs may cause cardiomyopathy.
Relating to or involving the heart and blood vessels. Use of some antiretroviral (ARV) drugs may increase the risk of cardiovascular disease.
Also known as: Chemokine Receptor 5
A protein on the surface of certain immune system cells, including CD4 T lymphocytes (CD4 cells). CCR5 can act as a coreceptor (a second receptor binding site) for HIV when the virus enters a host cell.
See Related Term(s): CCR5 Antagonist, Coreceptor, Fusion, Life Cycle
Also known as: CCR5 Inhibitor, CCR5 Receptor Blocker
Antiretroviral (ARV) HIV drug class. CCR5 antagonists block the CCR5 receptor on the surface of certain immune cells, such as CD4 T lymphocytes (CD4 cells). This prevents HIV from entering the cell.
See Related Term(s): CCR5, Drug Class
Also known as: CD4 Cell Count, CD4 T Lymphocyte Count
A laboratory test that measures the number of CD4 T lymphocytes (CD4 cells) in a sample of blood. In people with HIV, the CD4 count is the most important laboratory indicator of immune function and the strongest predictor of HIV progression. The CD4 count is one of the factors used to determine when to start antiretroviral therapy (ART). The CD4 count is also used to monitor response to ART.
See Related Term(s): CD4 Percentage, CD4 T Lymphocyte, HIV Progression
A protein found primarily on the surface of CD4 T lymphocytes (CD4 cells). To enter a host cell, HIV binds to a CD4 receptor and a coreceptor (either CCR5 or CXCR4) on the host cell.
See Related Term(s): CCR5, CD4 T Lymphocyte, CXCR4, Fusion, Life Cycle
Also known as: CD4 Cell, Helper T Cell
A type of lymphocyte. CD4 T lymphocytes (CD4 cells) help coordinate the immune response by stimulating other immune cells, such as macrophages, B lymphocytes (B cells), and CD8 T lymphocytes (CD8 cells), to fight infection. HIV weakens the immune system by destroying CD4 cells.
See Related Term(s): CD4 Count, CD4 Percentage, Lymphocyte, T Lymphocyte
CD4 T Lymphocyte Count
Also Known As: CD4 Count
A service of the Centers for Disease Control and Prevention (CDC) that disseminates health information on a wide variety of disease prevention and health promotion topics to the general public, health care providers, and partners worldwide. Information is available via the Web, phone, e-mail, and postal mail.
See Related Term(s): Centers for Disease Control and Prevention
Centers for Disease Control and Prevention-National Prevention Information Network (CDC-NPIN) 
(En español)
Also known as: National Prevention Information Network
A service of the Centers for Disease Control and Prevention (CDC) that disseminates information on HIV/AIDS, viral hepatitis, other sexually transmitted diseases, and tuberculosis (TB). Information is available via the Web, phone, e-mail, and postal mail.
See Related Term(s): Centers for Disease Control and Prevention
Centers for Medicare and Medicaid Services (CMS) (En español)
Also known as: Health Care Financing Administration
A federal agency that administers the Medicare program and monitors the Medicaid programs offered by each state, including the Children's Health Insurance Program.
Central Nervous System (CNS) (En español)
The part of the nervous system that is made up of the brain and spinal cord. The central nervous system (CNS) serves as the main processing center for the entire nervous system and coordinates all body functions. HIV infection or use of some antiretroviral (ARV) drugs can cause damage to the CNS.
Cerebrospinal Fluid (CSF) (En español)
A clear, nutrient-rich fluid that surrounds the brain and spinal cord. Cerebrospinal fluid (CSF) acts as a cushion, protecting the brain and spinal cord from injury.
A type of cancer that develops in the cervix. Cervical cancer is almost always caused by the human papillomavirus (HPV), which is spread through sexual contact. In women with HIV, invasive cervical cancer is an AIDS-defining cancer.
See Related Term(s): AIDS-Defining Cancer, Cervix, Human Papillomavirus
The lower, narrow end of the uterus (womb), which forms a canal between the uterus and vagina.
Delivery of a baby by a surgical incision through the mother's abdominal wall and uterus. In some pregnant women infected with HIV, a scheduled Cesarean delivery may reduce the risk of mother-to-child transmission of HIV.
See Related Term(s): Cesarean Section, Prevention of Mother-to-Child Transmission
Also known as: C-Section
Surgical incision through the abdominal wall and uterus to deliver a baby.
See Related Term(s): Cesarean Delivery
Also known as: American Trypanosomiasis, South American Trypanosomiasis
A disease caused by the parasite
Trypanosoma cruzi (a type of protozoa). Chagas disease is most commonly transmitted when people come into contact with the feces of an infected riduviid bug, a blood-sucking insect that feeds on humans and animals. In the earliest stage of infection, Chagas disease usually has few signs or symptoms. However, if untreated, the disease becomes a lifelong infection. In people with HIV, reactivation of chronic Chagas disease infection can cause inflammation of the brain and meninges (meningoencephalitis).
See Related Term(s): Opportunistic Infection
A sexually transmitted infection caused by the bacterium
Hemophilus ducreyi. Chancroid causes genital ulcers (sores), which increase the risk of HIV transmission.
Chemokine Receptor 4
Also Known As: CXCR4
Chemokine Receptor 5
Also Known As: CCR5
Small proteins secreted by cells to mobilize and activate infection-fighting white blood cells. Chemokines are involved in many immune and inflammatory responses.
Also known as: Chemoprophylaxis
Use of specific drugs, vitamins, or other substances to reverse, suppress, or prevent a disease.
Use of chemicals to treat a disease. Although chemotherapy is used to describe any therapy involving the use of chemical-based agents, most often it refers to the use of chemical-based agents to treat cancer.
Child-Turcotte-Pugh Classification System (En español)
Also known as: Child-Pugh Score
A classification system used to measure liver function, especially in people with chronic liver disease. The system may be used to assess liver function in people who have HIV/hepatitis C viurs (HCV) coinfection.
A common sexually transmitted infection caused by the bacterium
Chlamydia trachomatis. Chlamydia often has mild or no symptoms, but if left untreated, it can lead to serious complications, including infertility. Chlamydia may increase the risk of HIV transmission.
See Related Term(s): Sexually Transmitted Infection
Bile duct disease. (Bile ducts are tubes that carry bile from the gallbladder to the small intestine, where the bile is used to digest fats.) Cholangiopathy may occur as a complication of AIDS or may be caused by certain opportunistic infections.
A waxy, fat-like substance that is made by the liver or absorbed from animal food sources such as eggs, meat, and dairy products. The body uses cholesterol to insulate nerves, make cell tissues, and produce certain hormones. Excess cholesterol, however, can clog the arteries and lead to heart disease. Some antiretroviral (ARV) drugs may cause high cholesterol levels.
See Related Term(s): Atherosclerosis
A thread-like structure found within a cell. Chromosomes, which are made of DNA coiled around proteins, carry all of the genetic information essential to the life of the cell.
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) (En español)
A rare neurological disorder in which the immune system mistakenly attacks part of the peripheral nervous system. Chronic inflammatory demyelinating polyneuropathy (CIDP) primarily destroys the myelin that covers the peripheral nerves, causing the nerve signals to slow down. This damage can gradually weaken the legs and, to a lesser extent, the arms. CIDP has been associated with advanced HIV infection.
See Related Term(s): Myelin, Peripheral Nervous System
Pertaining to the area of the face around the mouth.
An antiretroviral (ARV) drug regimen that purposefully excludes all ARV drugs from a specific drug class. Class-sparing regimens are used to save specific ARV drugs for future use in case a regimen needs to be changed because of toxicity or drug resistance. A class-sparing regimen may also be used to avoid adverse effects associated with a specific drug class.
See Related Term(s): Drug Class
Causing breaks in chromosomes, which results in sections of a chromosome being deleted or rearranged. Before being approved, drugs—including antiretroviral (ARV) drugs—are tested to assess their potential for clastogenic effects.
See Related Term(s): Chromosome
An early notice of urgent findings from federally funded clinical trials. Clinical alerts are disseminated in a variety of ways, including online, to advise health care professionals and others of research findings that could affect patient care.
See Related Term(s): Clinical Trial
Also known as: Endpoint, Outcome Measure
In a clinical trial, an outcome or event used to objectively measure the effect of a drug or other intervention being studied. Common endpoints include severe toxicity, disease progression, and death.
See Related Term(s): Clinical Trial, Surrogate Endpoint
Advance of disease that can be measured by observable and diagnosable signs or symptoms. For example, HIV progression can be measured by change in CD4 count.
See Related Term(s): CD4 Count, HIV Progression
An online, searchable database of up-to-date information on thousands of federally and privately supported clinical trials for a wide range of diseases and conditions, including HIV infection. The site provides information about a trial's purpose, who may participate, study site locations, and contact information.
ClinicalTrials.gov is managed by the federal government.
See Related Term(s): Clinical Trial
Also known as: Peak Concentration
A pharmacokinetic measure used to determine drug dosing. Cmax is the highest concentration of a drug in the blood, cerebrospinal fluid, or target organ after a dose is given.
See Related Term(s): Cmin, Pharmacokinetics
Also known as: Trough Concentration, Trough Level
A pharmacokinetic measure used to determine drug dosing. Cmin is the lowest concentration of a drug in the blood, cerebrospinal fluid, or target organ after a dose is given.
See Related Term(s): Cmax, Pharmacokinetics
A disease or condition that affects the blood's ability to coagulate (clot) normally.
Difficulty thinking, reasoning, or remembering. Some people with HIV may have cognitive impairment.
A group of individuals with certain characteristics in common, such as age or disease risk factor. For example, participants for a clinical trial may be recruited from a particular cohort, such as women of child-bearing age, children under 5 years old, or males with high blood pressure.
See Related Term(s): Clinical Trial
When a person has two or more infections at the same time. For example, a person infected with HIV may be coinfected with hepatitis C (HCV) or tuberculosis (TB) or both.
See Related Term(s): Monoinfection
Inflammation of the colon (large intestine). Symptoms can include abdominal pain, nausea, and diarrhea. Colitis may be associated with HIV infection or related opportunistic infections.
Common Logarithm
Also Known As: Log10
Community Programs for Clinical Research on AIDS (CPCRA) (En español)
A federally sponsored program that conducts HIV-related clinical research through a national network of community-based research units. A primary objective of Community Programs for Clinical Research on AIDS (CPCRA) is to involve community-based primary care providers and their patients in HIV/AIDS research.
Community-Based Organization (CBO) (En español)
A public or private nonprofit organization that provides services to local community members of an identifiable group, such as people with HIV.
Also known as: Comorbid Condition
When a person has two or more diseases or conditions at the same time. For example, a person with high blood pressure may also have heart disease.
Complementary and Alternative Medicine (CAM) (En español)
Health care practices and products that are not considered part of conventional (Western) medicine. Complementary medicine refers to use of nonstandard treatments together with conventional treatments. Alternative medicine refers to use of nonstandard treatments in place of conventional treatments. Examples of complementary and alternative medicine (CAM) include use of herbal medicines, acupuncture, and massage therapy.
See Related Term(s): National Center for Complementary and Alternative Medicine
Complete Blood Count (CBC) (En español)
A blood test that measures the following components in a sample of blood: red blood cells, white blood cells, platelets, and hemoglobin. A complete blood count (CBC) with differential also measures the levels of the five types of white blood cells found in blood: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. The CBC is used to assess overall health and to diagnose and guide treatment of numerous diseases.
Comprehensive International Program of Research on AIDS (CIPRA) (En español)
A federal program that provides long-term support to developing countries to conduct HIV/AIDS research relevant to their populations.
Comprehensive Metabolic Panel (CMP) (En español)
Also known as: Basic Chemistry Profile
A blood test that measures several parameters, including blood sugar (glucose), proteins, electrolytes (such as sodium and potassium), waste products (such as blood urea nitrogen [BUN] and creatinine), and enzymes. The comprehensive metabolic panel is used to assess overall health and to diagnose and guide treatment of numerous diseases.
Sexual partners in which both partners are infected with a sexually transmitted infection, such as HIV.
See Related Term(s): Discordant Couple
Also known as: Prophylactic
A device used during sexual intercourse to block semen from coming in contact with the inside of the vagina. Condoms are used to reduce the likelihood of pregnancy and to prevent the transmission of sexually transmitted infections, including HIV. The male condom is a thin rubber cover that fits over a man’s erect penis. The female condom is a polyurethane pouch that fits inside the vagina.
Also known as: Pink Eye, Red Eye
Inflammation or infection of the conjunctiva, which is the mucous membrane that lines the inner surface of the eye. Conjunctivitis is commonly caused by a bacterial or viral infection, an allergic reaction, or a blocked tear duct (in babies). Conjunctivitis can also occur as part of a hypersensitivity reaction to certain antiretroviral (ARV) drugs.
Also known as: Contagious
An infectious disease that can be transmitted from person to person. Transmission can occur through direct physical contact, such as by touching or having sex with an infected person; through indirect contact, such as by touching or using an object that an infected person has touched or used; or through close proximity, such as being exposed to an infected person’s sneeze or cough.
See Related Term(s): Infectious Disease, Sexual Transmission
A symptom or condition that makes a particular treatment or procedure inadvisable because of potential for harm. There are two types of contraindications: relative and absolute.
See Related Term(s): Absolute Contraindication, Relative Contraindication
In a clinical trial, the group of participants that is not given the experimental treatment being studied. The control arm receives either the standard treatment for the disease or a placebo. The control arm is compared to the experimental treatment arm to determine whether the experimental treatment works.
See Related Term(s): Clinical Trial, Controlled Trial, Experimental Arm, Placebo
A type of clinical trial that includes a control arm. The control arm is compared to the experimental treatment arm to determine whether the experimental treatment works.
See Related Term(s): Clinical Trial, Control Arm, Experimental Arm
Also known as: HIV Viral Core
The bullet-shaped center of HIV. The viral core contains the genetic information (two single strands of RNA) and three enzymes needed for HIV to replicate.
See Related Term(s): p24
A protein on the surface of a cell that serves as a second binding site for a virus or other molecule. In order to enter a host cell, HIV must bind to two sites on the cell: the primary CD4 receptor and either the CCR5 or CXCR4 coreceptor.
See Related Term(s): CCR5, CXCR4, Receptor
Resistance to one or more drugs that occurs as a result of previous exposure to a similar drug. For example, HIV resistance to one non-nucleoside reverse transcriptase inhibitor (NNRTI) drug may produce resistance to
all drugs in the NNRTI drug class, including drugs never used. Excluding all drugs in a drug class from an HIV regimen (drug sparing) is a strategy used to prevent cross resistance.
See Related Term(s): Class-Sparing Regimen, Drug Resistance
A sensitivity reaction to a drug that predisposes a person to react similarly to a different, but related, drug. For example, a person who has an allergic reaction to penicillin may also have an allergic reaction to amoxicillin, a related antibiotic.
Also known as: Cryoablation
A minimally invasive treatment in which liquid nitrogen or argon gas is used to freeze and destroy diseased tissue.
A life-threatening infection caused by the fungus
Cryptococcus neoformans, which infects the membranes surrounding the brain and spinal cord. Symptoms include fever, malaise, and headache. Cryptococcal meningitis most often affects people with weakened immune systems, including people with HIV. In people with HIV, cryptococcal meningitis is an AIDS-defining condition.
See Related Term(s): AIDS-Defining Condition, Opportunistic Infection
Also known as: Torulosis
An infection caused by the fungus
Cryptococcus neoformans. The fungus enters and infects the body through the lungs. Cryptococcosis may go away on its own, remain in the lungs, or spread throughout the body (disseminate). Most cases of cryptococcosis are in people with weakened immune systems, such as people with HIV. In people with HIV, cryptococcosis is an AIDS-defining condition.
See Related Term(s): AIDS-Defining Condition, Cryptococcal Meningitis, Opportunistic Infection
Also known as: Crypto
An infection caused by the protozoan
Cryptosporidium. Symptoms of cryptosporidiosis include diarrhea, nausea, vomiting, and lower abdominal cramping. In people with weakened immune systems, such as people with HIV, cryptosporidiosis can lead to severe and life-threatening loss of muscle and body mass and malnutrition. In people with HIV, chronic cryptosporidiosis (lasting more than 1 month) is an AIDS-defining condition.
See Related Term(s): AIDS-Defining Condition, Cryptosporidium, Opportunistic Infection
The protozoan parasite that causes the diarrheal disease cryptosporidiosis.
Cryptosporidium lives in the intestines of infected animals and humans and may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals.
See Related Term(s): Cryptosporidiosis, Protozoan
Crystals in the urine. (Crystals are tiny stones composed of chemicals such as calcium.) Use of antiretroviral (ARV) drugs may cause crystalluria.
Also known as: Chemokine Receptor 4, Fusin
A protein on the surface of certain immune system cells, including CD4 T lymphocytes (CD4 cells). CXCR4 can act as a coreceptor (a second receptor binding site) for HIV when the virus enters a host cell.
See Related Term(s): Coreceptor, Fusion, Life Cycle
Also known as: Cytochrome P450 3A4
An enzyme that plays a key role in the metabolism of approximately half the drugs in use today. CYP3A4 is a member of the cytochrome P450 family of enzymes.
See Related Term(s): Cytochrome P450
Cytochrome P450 (CYP450) (En español)
A group of enzymes involved in the breakdown of drugs in the liver. Many drugs can inhibit or enhance the activity of these enzymes, causing drug levels in the blood to increase or decrease. Cytochrome P450 (CYP450) enzymes metabolize all protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) and can cause drug interactions that may result in adverse effects.
See Related Term(s): Drug Interaction
Cytochrome P450 3A4
Also Known As: CYP3A4
A family of proteins produced by cells, especially by immune cells. Cytokines act as chemical messengers between cells to regulate immune responses.
See Related Term(s): Interferon, Interleukin-2, Interleukin-7
A herpesvirus that can cause infection in many parts of the body. Typically, only people with weakened immune systems become seriously ill from cytomegalovirus (CMV) infection. In people with HIV, CMV can cause serious illnesses, including pneumonia (infection of the lungs), gastroenteritis (infection of the gastrointestinal tract), encephalitis (inflammation of the brain), or retinitis (infection of the eye). CMV infection that affects a body part other than the liver, spleen, or lymph nodes is an AIDS-defining condition in people with HIV.
See Related Term(s): Cytomegalovirus Retinitis, Herpesviruses
A lower-than-normal number of blood cells, including red blood cells, white blood cells, or platelets.
Having the ability to kill cells.