Glossary of AIDS

From WikiMD's Wellness Encyclopedia

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Stylized rendering of a cross-section of the Human Immunodeficiency Virus
HIV virion structure
HIV
HIV budding
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HIV infected H9 T cell

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  • Accidental inoculation An occupational exposure to HIV that occurs during the performance of job duties (by a nurse or doctor, for example). Includes a needlestick or cut with a sharp object, contact of mucous membranes (mouth, eyes), or contact of skin (especially when the exposed skin is chapped, abraded, or afflicted with dermatitis--skin rash or sores--or the contact is prolonged or involves an extensive area) with blood, tissues, or other body fluids (stool, urine, vaginal secretions, saliva, mucous) to which universal precautions apply.
  • Acquired immunodeficiency syndrome (AIDS) The most severe manifestation of infection with the human immunodeficiency virus (HIV). The Centers for Disease Control and Prevention (CDC), the World Health Organization, and many national governments list numerous opportunistic infections and cancers that, in the presence of HIV infection, result in an AIDS diagnosis. AIDS is also defined on the basis of the degree of immunodeficiency in an individual with HIV infection.
  • Active immunity Protection from a disease as a result of previous exposure to the disease-causing infectious agent or part of the infectious agent (antigen). The protection can be a result of having had the disease or having received a vaccine to prevent getting the disease.
  • Active tuberculosis (TB) Active disease caused by Mycobacterium tuberculosis, as evidenced by a confirmatory culture, or, in the absence of culture, suggestive clinical symptoms, including productive cough lasting >3 weeks, chest pain, hemoptysis, fever, night sweats, weight loss, and easy fatigability. Active TB is a communicable disease that is treatable, curable, and preventable. Persons with active TB disease should be under the care of a health care provider. Active TB disease may indicate immune deficiency. For people with HIV, active TB disease is considered an opportunistic infection and a qualifying condition for an AIDS diagnosis.
  • Acute HIV infection The period following infection when there is rapid production of virus. An estimated 80% to 90% of individuals with primary HIV infection develop an acute syndrome (disorder) characterized by flulike symptoms of fever, fatigue, swollen lymph nodes, sore throat, headache, aching muscles, and sometimes skin rash. Following infection, the immune system produces antibody and a cellular response to the virus (seroconversion) and a broad HIV-specific immune response occurs, usually within an average of 3 weeks after HIV infection. High levels of virus (HIV RNA) can be found in the blood during this time.
  • Adherence The extent to which a patient takes the agreed-upon medication or other treatment as prescribed.
  • Adjuvant An ingredient added to a prescription or solution that increases or modifies the action of the principal ingredient. May be used in treatment of HIV or for HIV vaccines.
  • Adverse reaction (Adverse event) An unwanted effect caused by the administration of drugs or vaccines. Onset may be sudden or develop over the course of time. See Side effects.
  • Aerosolized A form of administering a drug in which the drug, such as pentamidine, is turned into a fine spray or mist by a nebulizer and inhaled.
  • Agammaglobulinemia A nearly total absence of antibodies (immunoglobulins) resulting in loss of the ability to produce immune antibodies. See Antibody.
  • AIDS-related cancer Any of several cancers that are more common or more aggressive in persons living with HIV. These malignancies include certain types of immune system cancers known as lymphomas, Kaposi sarcoma, and anogenital cancers that primarily affect the anus and the cervix.
  • Alanine aminotransferase (ALT) A liver enzyme that plays a role in protein metabolism. Abnormally high blood levels of ALT are a sign of liver inflammation or damage from infection or drugs. A normal level is below approximately 50 IU/L.
  • Alkaline phosphatase An enzyme normally present in certain cells within the liver, bone, kidney, intestine, and placenta. When the cells are destroyed in those tissues, more of the enzyme leaks into the blood, and levels rise in proportion to the severity of the condition. Measurement of this enzyme is used as an indication of the health of the liver.
  • Alopecia Loss of hair that frequently occurs in patients undergoing treatment for cancer or suffering from certain other diseases, in which cell-killing, or cytotoxic, drugs are used.
  • Alternative medicine A broad category of treatment systems (eg, chiropractic, herbal medicine, acupuncture, homeopathy, naturopathy, and spiritual devotions) or culturally based healing traditions such as Chinese, Ayurvedic, and Christian Science. Alternative medicine approaches often are not accepted by the biomedical (ie, mainstream Western) establishment. Alternative medicine also is referred to as "complementary medicine." The designation "alternative medicine" is not equivalent to holistic medicine, a narrower term.
  • Alternative test site A site that provides only HIV services. Sometimes referred to as an anonymous test site.
  • Amebiasis An inflammation of the intestines caused by infection with Entamoeba histolytica (a type of ameba) and characterized by frequent, loose stools flecked with blood and mucus.
  • Anal intercourse/Anal sex A type of sexual intercourse in which a man inserts his penis in his partner's anus. Anal sex can be insertive or receptive.
  • Anemia A lower than normal number of red blood cells.
  • Anergy The loss or weakening of the body's immunity to an irritating agent, or antigen. Patients may be so immunodeficient that they are unable to produce a reaction to an infectious agent. For example, such patients usually will not test positive for tuberculosis (TB) on a tuberculin skin test (or Mantoux test).
  • Anogenital Related to the anal (rectum) and/or genital (sexual) area of the body.
  • Anonymous Without an ability to identify a person. In anonymous testing, patient-identifying information is not linked to testing information, including the request for tests or test results.
  • Anorexia The lack or loss of appetite that leads to significant decline in weight.
  • Antenatal The period between conception and birth. Same as prenatal.
  • Antibiotic A natural or manufactured substance that prevents the growth of bacteria or fungi. Some antibiotics are used to treat infectious diseases.
  • Antibody Substances in the blood or other body fluids that destroy bacteria, viruses, or other harmful agents (antigens). They are members of a class of proteins known as immunoglobulins, which are produced by special white blood cells called B-lymphocytes.
  • Antibody-mediated immunity Also called humoral immunity. Immunity that results from the activity of antibodies in blood and lymphoid tissue.
  • Antifungal A substance that kills or slows the growth of a fungus.
  • Antigen A substance that, when introduced into the body, stimulates production of an antibody.
  • Antineoplastic A substance that prevents the development or growth of cancer cells.
  • Antiprotozoal A substance that kills or inhibits the growth of single-celled microorganisms called protozoa.
  • Antiretroviral A substance that kills or suppresses a retrovirus, such as HIV.
  • Antiretroviral drugs Substances used to kill or stop the multiplication of retroviruses such as HIV.
  • Antiretroviral therapy (ART) Combination antiretroviral regimens that aggressively decrease HIV viral multiplication to halt the progress of HIV disease. The usual ART regimen combines three or more different drugs. These treatment regimens can reduce the amount of virus so that it becomes undetectable in a patient's blood.
  • Antiviral A substance or process that destroys a virus or suppresses its replication (ie, reproduction).
  • Aphthous ulcer A painful mouth or throat sore of unknown cause. Aphthous ulcers are common in persons living with HIV.
  • Approved drugs In the United States, the Food and Drug Administration (FDA) and similar government departments must approve a substance as a drug before it can be marketed.
  • Aspergillosis A fungal infection--resulting from the fungus Aspergillus--of the lungs that can spread through the blood to other organs. Symptoms include fever, chills, difficulty in breathing, and coughing up blood.
  • Assay A qualitative or quantitative analysis of a substance; a test.
  • Asymptomatic Without symptoms or not sick. Usually used in HIV/AIDS literature to describe a person who has HIV infection but who shows no clinical symptoms of the disease and who is not sick. Even though a person is asymptomatic, he or is still undergoing damage to the immune system and may still infect another person with HIV.
  • Attenuated Weakened or decreased. For example, an attenuated virus can no longer produce disease but might be used to produce a vaccine.

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  • B lymphocytes (B cells) One of the two major classes of lymphocytes (white blood cells); they are involved in the production of antibodies.
  • BCG Bacille Calmette-Guerin--a TB vaccine.
  • BID Twice each day.
  • Biopsy Surgical removal of a piece of tissue from a person for microscopic examination to make a diagnosis (eg, to determine whether abnormal cells such as cancer cells are present).
  • Bisexual Having sexual relations with both females and males.
  • BIW Twice each week.
  • Blinded study A clinical research study in which participants are unaware as to whether they are receiving the experimental drug or a placebo (or another drug). See Double-blind study.
  • BMI Body mass index (kilogram/meter2).
  • Body fluids Any fluid in the human body, such as blood, urine, saliva (spit), sputum, tears, semen, mother's milk, or vaginal secretions. Only blood, semen, mother's milk, and vaginal secretions have been linked directly to the transmission of HIV.
  • Body surface area (BSA) A measure of the overall surface of a person calculated from height and weight. Body surface area is expressed in meters squared (m2).
  • Booster A second or subsequent dose of a vaccine given to increase the immune response to the original dose.
  • Branched DNA assay (bDNA test) A test developed by Bayer for measuring the amount of HIV (as well as other viruses) in blood plasma. Test results are calibrated in numbers of virus particle equivalents per milliliter of plasma.
  • Breakthrough infection An infection caused by the infectious agent the substance is designed to protect against. As it pertains to a vaccine trial, the infection may be caused by exposure to the infectious agent, such as HIV, before the vaccine has taken effect, before all doses of the vaccine have been given, or as a result of the vaccine not being effective.
  • Bronchoscopy Examination of the bronchial (lung) passages through the tube of an endoscope (usually a curved flexible tube containing fibers that carry light down the tube and project an enlarged image up the tube to the viewer) that is inserted into the upper lungs.

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  • Cachexia Emaciation, extreme thinness. Cacexia reflects malnutrition and general ill health. It usually is associated with serious disease. See Wasting syndrome.
  • Candida Yeastlike fungi commonly found in the normal flora of the mouth, skin, intestinal tract, and vagina. It can become infectious in individuals with an abnormal immune system. See Candidiasis; Fungus; Thrush.
  • Candidiasis An infection with a yeastlike fungus of the Candida family, generally Candida albicans. Candidiasis of the esophagus, trachea, bronchi, or lungs is an indicator disease for AIDS. Oral or recurrent vaginal candida infection is an early sign of immune system abnormalities. See Opportunistic infection; Thrush; Vaginal candidiasis.
  • Casual contact Can be defined as normal day-to-day contact among people at home, school, work, or in the community. Some contagious infectious agents (eg, chickenpox, flu) can be transmitted by casual contact, but HIV cannot.
  • CD4 (T4) or CD4+ cells A type of lymphocyte involved in protecting against viral, fungal, and protozoal infections. They are also known as T helper cells or simply T cells. HIV infects and destroys CD4 lymphocytes. Destruction of CD4+ lymphocytes is the major cause of the immunodeficiency observed in AIDS, and decreasing CD4 lymphocyte levels are the best indicator of someone's risk of developing opportunistic infections.
  • CD4 count A test that measures the number of CD4 lymphocytes in the blood, thus reflecting the state of the immune system. A normal count in a healthy adult is 600-1,200 cells/µL. When the CD4 count of an adult falls below 200 cells/µL, there is a high risk of opportunistic infection.
  • CD4, CD4 receptor One of the protein structures on the surface of a human cell that allows HIV to attach, enter, and thus infect the cell. Present on CD4 cells (helper T lymphocytes) among others.
  • CD8 (T8) cells White blood cells (lymphocytes) with the CD8 protein on their surface. These white blood cells kill some cancer cells and cells infected by bacteria and viruses. Also called cytotoxic T cells, T8 cells, cytotoxic T lymphocytes.
  • Cervical dysplasia Abnormality in the size, shape, and organization of adult cells of the cervix. It is often found before cancer cells appear. A precursor lesion for cervical cancer. Studies indicate an increase of cervical dysplasia among women living with HIV.
  • Cervical intraepithelial neoplasia (CIN) An abnormality of the epithelium (lining) of the cervix, often precancerous. Considerable evidence implicates a virus called human papilloma virus (HPV) in the development of CIN.
  • Chancroid A highly contagious sexually transmitted disease caused by the Haemophilus ducreyi bacterium with symptoms appearing 3 to 5 days after exposure.
  • Chemokines Chemokines are messenger molecules secreted by CD8 cells whose major function is to attract immune cells to sites of infection. Several chemokines--called RANTES, MIP-1A, and MIP-1B--interfere with HIV multiplication by occupying these receptors.
  • Chemotherapy In general, chemotherapy refers to the use of medicines to treat any disease. It is more commonly used to describe medicines to treat cancer.
  • Chlamydia A sexually transmitted disease (STD) caused by Chlamydia trachomatis that infects the genital tract. The infection is frequently asymptomatic (ie, shows no symptoms), but if left untreated, it can cause sterility in women.
  • Clinical Pertaining to observations, tests, or treatment of patients.
  • Clinical latency The period of time during which a virus or bacteria or other organism is living or developing in the body without causing symptoms. The period of time in which a person with HIV infection does not exhibit any evidence of disease or sickness.
Time course
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Monotherapy levels
AIDS cases worldwide
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AIDS in Africa
Causes of death in the United States
  • Clinical trial A scientifically designed study of the effects of a drug, vaccine, biologic, or behavior in humans. The goal is to define the safety, the benefit, and side effects of the treatment or intervention. Most countries require strict testing of all new drugs and vaccines prior to their approval for use.
  • Coccidioidomycosis An infectious fungal disease caused by the breathing in of Coccidioides immitis, which are carried on windblown dust particles.
  • Cohort A group of individuals with some characteristics in common.
  • Colitis Inflammation of the colon, the lower part of the intestine.
  • Colostrum The first thick yellow milk secreted by a woman beginning lactation. Colostrum contains high levels of proteins and antibodies.
  • Combination therapy Two or more drugs or treatments used together to obtain the best results against HIV or another infection. Combination drug therapy (treatment) is recommended for all persons with HIV.
  • Commercial sex worker (CSW) A woman or man who offers sexual intercourse for a fee. The terms prostitute or prostitution are used more frequently outside the HIV/AIDS field.
  • Community planning Community planning groups are responsible for developing HIV prevention, treatment, and care plans that are used in their communities. The goal of HIV community planning is to improve the effectiveness of HIV programs and to be certain that the needs of the community are being met.
  • Complete blood count (CBC) A frequently ordered blood test that provides the white and red blood cell count, hematocrit, and hemoglobulin in a microliter of whole blood.
  • Concomitant drugs Drugs that are taken together. Taking certain concomitant medications may cause adverse interactions.
  • Condyloma A wartlike skin growth usually on the external genitalia or perianal area.
  • Condyloma acuminatum A wart in the genital and perianal area. Although the lesions are usually few in number, they may aggregate to form large cauliflower-like masses. Caused by the human papillomavirus (HPV), it is infectious and capable of being transmitted from one part of the body to another). Also called genital warts, venereal warts, or verruca acuminata.
  • Confidentiality Relating to a piece of information about a person that should not be given to another person without that person's permission. An example would be the result, whether positive or negative, of an HIV test.
  • Confirmatory test A second test, to show that the result of a previous test was correct. Because the diagnosis of HIV infection is so important, a second (confirmatory) test, is done. The confirmatory test should be of a different type than the first test.
  • Confirmed positive For HIV, a blood sample that is positive on an initial ELISA test, repeatedly positive on a second ELISA run on the same specimen, or confirmed positive on Western blot or other supplemental test that indicates the client is infected.
  • Contagious Any infectious disease capable of being transmitted by direct or indirect contact from one person to another.
  • Contraindication Any condition that renders a particular line of treatment improper or undesirable. Some drugs may be contraindicated when given together (eg, zidovudine and lamivudine).
  • Controlled clinical trials A study performed in humans in which a control is used. A control is a standard against which study observations may be evaluated. For example, in clinical trials, one group of patients is given an experimental drug, while another group (ie, the control group) is given either the normal treatment for the disease or a placebo.
  • Cotrimoxazole Also known as trimethoprim/sulfamethoxazole, Bactrim, Septra, or TMP/SMX. A combination antibiotic drug effective at preventing and treating Pneumocystis jiroveci pneumonia (PCP or PJP); also serves as a prophylaxis against toxoplasmosis. The drug is also active against certain bacterial infections. See Trimethoprim/sulfamethoxazole.
  • Counseling Confidential dialogue between individuals and their health care providers. The term can refer to discussions between health care workers and clients/patients specific to HIV testing to help clients examine their risk of acquiring or transmitting HIV infection.
  • Creatinine A protein found in muscles and blood, and excreted by the kidneys in urine. The level of creatinine in the blood or urine provides an indication of kidney function.
  • Cross-resistance The process in which an infectious agent that acquires resistance to one drug through direct exposure also turns out to have resistance to one or more other drugs to which it has not been exposed.
  • 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. See Cryptococcus neoformans.
  • Cryptococcosis An infectious disease caused by the fungus Cryptococcus neoformans that is acquired via the respiratory tract. It can spread from the lungs to the central nervous system (especially the membranes surrounding the brain), the skin, the skeletal system, and the urinary tract. It is considered an AIDS-defining opportunistic infection in persons infected with HIV. See Cryptococcal meningitis.
  • Cryptococcus neoformans A fungus found in soil contaminated by bird droppings. Most people have been exposed to this organism, which does not usually cause disease in healthy people. In persons with AIDS, this organism can cause illness and death.
  • Cryptosporidiosis A diarrheal disease caused by the protozoa Cryptosporidium that grows in the intestines. Symptoms include abdominal cramps and severe chronic diarrhea. It is considered an AIDS-defining opportunistic infection in persons with HIV infection as immunological deterioration progresses.
  • Cryptosporidium The protozoan (parasite Cryptosporidium parvum), which causes cryptosporidiosis. The parasite 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. The parasite grows in the intestines and, in people with HIV disease, causes cryptosporidiosis. See Cryptosporidiosis.
  • Cutaneous Of, pertaining to, or affecting the skin.
  • Cytomegalovirus (CMV) A common herpes virus that is a common cause of opportunistic diseases in persons with AIDS and other persons with immune suppression. CMV has infected most adults; however the virus does not cause disease in healthy people. Because the virus remains in the body for life, it can cause disease if the immune system becomes severely damaged by drugs. While CMV can infect most organs of the body, persons with AIDS are most susceptible to CMV retinitis (disease of the eye) and colitis (disease of the colon). See Cytomegalovirus (CMV) retinitis.
  • Cytomegalovirus (CMV) retinitis An eye disease caused by the CMV virus, common among persons who are living with HIV. Without treatment, persons with CMV retinitis can lose their vision. CMV infection can affect both eyes and is the most common cause of blindness among persons with AIDS. See Cytomegalovirus (CMV).
  • Cytopenia Deficiency in the cellular elements of the blood.
  • Cytotoxic An agent or process that is toxic or destructive to cells.
  • Cytotoxic T lymphocyte (CTL) A lymphocyte (white blood cell) that is able to kill foreign cells marked for destruction by the cellular immune system. CTLs can destroy cancer cells and cells infected with viruses, fungi, or certain bacteria. CTLs are also known as killer T cells; they carry the CD8 marker.

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  • Dementia Chronic impairment of thinking (ie, loss of mental capacity) that affects a person's ability to function in a social or occupational setting. See HIV-associated dementia (HAD).
  • Demyelination Destruction, removal, or loss of the myelin sheath of a nerve or nerves.
  • Dendritic cells Immune system cells that may initiate HIV infection by carrying the virus from the site of the infection to the lymph nodes, where other cells, such as CD4 T cells, become infected. Dendritic cells circulate through the body and bind to infectious agents in tissues, such as the skin and membranes lining the intestinal tract, lungs, and reproductive tract. Once in contact with CD4 T cells, they initiate an immune response to the virus.
  • Deoxyribonucleic acid (DNA) The twisted double-stranded molecular chain found in genes within the nucleus of each cell. DNA carries the genetic information that enables cells to reproduce and transmit hereditary characteristics.
  • Desensitization Gradually increasing the dose of a medicine in order to overcome severe reactions.
  • Diagnosis The decision that a patient has a specific disease or infection, usually accomplished by evaluating clinical symptoms and laboratory tests.
  • Dormant Inactive infection that is still present in the body.
  • DOT Directly observed therapy (short course). Treatment that is given under the observation of a health care worker.
  • Double-blind study A clinical trial design in which neither the patient nor the study staff know which patients are receiving the experimental drug and which are receiving a placebo (or another therapy).
  • Drug resistance The ability of some disease-causing infectious agents, such as bacteria and viruses, to adapt themselves, grow, and multiply even in the presence of drugs that usually kill them. See Cross-resistance.
  • Drug-drug interaction A change in the effect of a drug when administered with another drug. The effect may be an increase or a decrease in the action, or it may be an adverse effect that is not normally associated with either drug.
  • Dysplasia Any abnormal development of tissues or organs.
  • Dyspnea Difficult or labored breathing.

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  • Efficacy The maximum ability of a drug or treatment to produce a result regardless of the drug dosage.
  • EIA Enzyme-linked immunosorbent assay. See ELISA.
  • ELISA (Enzyme-linked immunosorbent assay) A type of enzyme immunoassay to determine the presence of antibodies to HIV in the blood or oral fluids. Repeatedly (i.e., two or more) reactive ELISA test results should be confirmed with a second, different test such as a rapid HIV test, or a DNA or RNA polymerase chain reaction (PCR). Availability of the confirmatory test often determines which one is performed.
  • Encephalitis A brain inflammation of viral or other infectious disease origin. Symptoms include headaches, neck pain, fever, nausea, vomiting, and nervous system problems. Several types of opportunistic infections can cause encephalitis.
  • Endemic Pertaining to diseases associated with particular locations or population groups.
  • Endoscopy Viewing the inside of a body cavity (e.g., colon or throat) with an endoscope, a device using flexible fiber optics.
  • Endotoxin A toxin present inside a bacterial cell.
  • Endpoint A category of data used to compare the outcome of a clinical trial. Common endpoints are severe toxicity, disease progression, or death.
  • End-stage disease Final period or phase in the course of a disease leading to a person's death.
  • Enteric Pertaining to the intestines.
  • Entry inhibitors Compounds designed to prevent the interactions between the HIV virus and the cell surface. These compounds can block or prevent HIV from binding to human cell surface receptors.
  • Eosinophil A type of white blood cell, called granulocyte, that can digest infectious agents.
  • Eosinophilia The formation and accumulation of an abnormally large number of eosinophils in the blood. Eosinophils are a type of white blood cell that helps to destroy infectious agents. Increased numbers are seen in allergy and parasitic infection.
  • Epidemic A disease that spreads rapidly through a part of the human population--such as within a given geographic area, a military base, school, or village--or persons of a certain age group or sex, such as the children or women within a region. Epidemic diseases can be spread from person to person or from a contaminated source such as food or water.
  • Epidemiologic surveillance The ongoing organizing and collection, analysis, and interpretation of facts about a disease or health condition.
  • Epidemiology The branch of medical science that deals with the study and distribution and control of a disease in a population.
  • Epithelium The covering of the internal and external organs of the body. Also the lining of blood vessels, body cavities, glands, and organs.
  • Epstein-Barr virus (EBV) A herpes-like virus that causes one of the two kinds of mononucleosis (the other is caused by CMV). It infects the nose and throat and is contagious. It has been associated with Burkitt lymphoma and hairy leukoplakia.
  • Erythema Redness or inflammation of the skin or mucous membranes.
  • Erythema multiforme A type of hypersensitivity reaction (rash) that occurs in response to drugs, infections, or illness. The exact cause is unknown. A severe form of this condition is called Stevens-Johnson syndrome.
  • Erythrocyte sedimentation rate (ESR) A test that measures the rate at which red blood cells settle through a column of liquid. This test is used to detect and monitor inflammation in the body.
  • Erythrocytes Red blood cells whose major function is to carry oxygen to cells.
  • Etiology The study or theory of the factors that cause disease.
  • Evaluation The study of a patient to determine the cause and effect of an illness, the study of a set of facts to determine what the facts mean, or the study of a program to determine its effectiveness.
  • Exclusion/Inclusion criteria The medical determining of whether a patient may or may not be allowed to participate in a clinical trial. For example, some trials may include persons with chronic liver disease, or may exclude persons with certain drug allergies.
  • Exclusive breast-feeding Feeding an infant only breast milk from the mother or a wet nurse, or expressed breast milk and no other liquids or solids with the exception of drops or syrups consisting of vitamins, mineral supplements, or medicines.
  • Exogenous Developed or originating outside the body.

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  • Failure to thrive (FTT) Weight loss or gradual but steady deterioration in weight gain as compared with the expected growth, as indicated in a child's growth chart.
  • False negative A test result that is not correct. This may be a result of performing the test incorrectly or using a test that is not accurate. A false-negative test result in HIV would be a result that is negative in a person who is actually infected.
  • False positive A test result that is not correct. This may be a result of performing the test incorrectly or using a test that is not accurate. A false-positive test result in HIV would be a result that is positive in a person who is not infected. For this reason, a second confirmatory test is recommended when a person tests HIV positive.
  • Fat redistribution Changes in body fat distribution, sometimes referred to as "lipodystrophy syndrome" or "fat redistribution syndrome," have been observed in patients taking antiretroviral medications (but are not necessarily caused by antiretrovirals). Changes may include abdominal fat accumulation, fat accumulation over the back of the neck ("buffalo hump"), wasting of legs and arms with prominence of the veins, facial thinning, and breast enlargement. See Lipodystrophy.
  • Food and Drug Administration (FDA) The U.S. Department of Health and Human Services agency responsible for ensuring the safety and effectiveness of all drugs, biologics, vaccines, and medical devices, including those used in the diagnosis, treatment, and prevention of HIV infection, AIDS, and AIDS-related opportunistic infections.
  • Fungus One of a group of primitive, nonvascular organisms including mushrooms, yeasts, rusts, and molds.
  • Fusion Inhibitor A class of antiretroviral agents that binds to the HIV envelope protein and blocks the structural changes necessary for the virus to fuse with the host CD4 cell. Enfuvirtide (T-20) is a drug in this class.

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  • Gay Having sexual relations with an individual of the same sex. Usually refers to male-male relations. The term lesbian is most often used for female-female sexual relationships.
  • Genital ulcer disease Ulcerative lesions on the genitals usually caused by a sexually transmitted disease such as herpes, syphilis, or chancroid. The presence of genital ulcers may increase the risk of transmitting HIV.
  • Genitals The area of the sexual organs. In the male, the penis and scrotum. In the female, the vulva and vagina.
  • Genitourinary tract The organs concerned with the production and excretion of urine and those concerned with reproduction. Also called genitourinary system, urogenital system, or urogenital tract.
  • Genotype The genetic makeup of an individual organism such as HIV. In reference to HIV, genotypic resistance testing determines whether the HIV genetic structure contains certain mutations that make it resistant to a drug. Contrast with Phenotype.
  • Giardiasis A common protozoal infection of the small intestine, spread via contaminated food and water and direct person-to-person contact.
  • Globulins Simple proteins found in the blood serum containing various substances that function in the immune system. See Immunoglobulin (Ig).
  • Gonorrhea An infection caused by Neisseria gonorrhoeae. Although gonorrhea is considered primarily a sexually transmitted disease, it also can be transmitted to newborns during the birth process.
  • Granulocyte A type of white blood cell filled with granules of compounds that digest infectious agents. Granulocytes are part of the innate immune system and have broad-based activity.
  • Granulocytopenia A lack or low level of granulocytes in the blood. Often used interchangeably with neutropenia.

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  • Harm reduction A prevention activity that aims to provide services to people with HIV and their sex and needle-sharing partners so they can reduce their risk of infection or, if already infected, prevent transmission of HIV to others. It also involves helping partners gain earlier access to individualized counseling, HIV testing, medical evaluation, treatment, and other prevention and support services.
  • HCW Health care worker.
  • Helper T cells Lymphocytes bearing the CD4 marker that are responsible for many immune system functions, including turning antibody production on and off. See CD4 (T4) or CD4+ cells.
  • Helper/Suppressor ratio (of T cells) T cells are lymphocytes (white blood cells) that are formed in the thymus and are part of the immune system. They have been found to be abnormal in persons with AIDS. The normal ratio of helper T cells (also known as CD4+ T cells) to suppressor T cells (also known as CD8+ T cells) is approximately 2 to 1. This ratio becomes inverted in persons with AIDS but also may be temporarily abnormal for other reasons.
  • Hematocrit A laboratory measurement of the percentage of packed red blood cells in a given volume of blood. In women, red blood cells are normally 37 to 47 percent of their blood, and in men, red blood cells are normally 40 to 54 percent of their blood.
  • Hemoglobin (HGB) The red, iron-based pigment in red blood cells that enables them to transport oxygen; normal hemoglobin values are 14-18 g/dL in men and 12-16 g/dL in women. Normal values in resource-poor countries may be lower.
  • 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 four major types of viral hepatitis: A, B, C, and D.
  • Hepatitis A Caused by infection with the hepatitis A virus, which is spread by fecal-oral contact.
  • Hepatitis B Caused by infection with the hepatitis B virus (HBV), which is most commonly passed to a partner during sexual intercourse, especially during anal sex, as well as through sharing of drug needles.
  • Hepatitis C Caused by infection with the hepatitis C virus, which is most commonly passed through sharing of drug use equipment; it also can be passed to a partner during sexual intercourse, especially during anal sex. Approximately 40% of patients infected with HIV are also infected with the hepatitis C virus (HCV), mainly because both viruses share the same routes of transmission.
  • Hepatotoxicity Liver damage due to toxic effects of poisons or drugs. Early damage is usually detected by measuring liver enzymes.
  • Herpes simplex virus 1 (HSV-1) A virus that causes cold sores or fever blisters on the mouth or around the eyes, and can be transmitted to the genital region. Stress, trauma, other infections, or suppression of the immune system can reactivate the latent virus.
  • Herpes simplex virus 2 (HSV-2) A virus causing painful sores of the anus or genitals that may lie dormant in nerve tissue. It can be reactivated to produce symptoms. HSV-2 may be transmitted to a newborn during birth from an infected mother, causing retardation and/or other serious complications.
  • Herpes varicella-zoster virus (VZV) The varicella virus causes chickenpox in children and may reappear in adults as herpes zoster. Also called shingles, herpes zoster consists of very painful blisters on the skin that follow nerve pathways.
  • Herpes viruses A group of viruses that includes herpes simplex type 1 (HSV-1), herpes simplex type 2 (HSV-2), Cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella-zoster virus (VZV), human herpes virus type 6 (HHV-6), and HHV-8, a herpes virus associated with Kaposi sarcoma. See entries under names of some of the individual viruses.
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Man giving blood for an AIDS test
Anti-AIDS drug AZT
  • Herpes zoster A painful infection with the varicella virus that normally causes chickenpox. The virus may be dormant for many years in the cells of the nervous system. When reactivated, it appears on the skin in various locations as painful sores. Also called shingles.
  • High-risk behavior A reported sexual, injection drug use, or other non-work-related HIV exposure that might put a patient at high risk of acquiring HIV infection.
  • Histoplasmosis A fungal infection, commonly of the lungs, caused by the fungus Histoplasma capsulatum. This fungus is commonly found in bird and bat droppings. It is spread by breathing in the spores of the fungus. Persons with severely damaged immune systems, such as those with AIDS, are susceptible to a very serious disease known as progressive disseminated histoplasmosis.
  • HIV prevention counseling Provision of information on how HIV is transmitted, how an individual becomes infected, and how to prevent infection. Encompasses all modes of transmission including sexual activity (heterosexual, homosexual and bisexual), intravenous drug use, mother-to-child transmission, breast feeding, accidental exposure from an infected patient, and HIV-infected blood transfusion.
  • HIV set point The point at which the level of virus stabilizes and remains at a particular level in each individual after the period of primary infection.
  • HIV-associated dementia (HAD) Previously referred to as AIDS dementia complex (ADC). A degenerative (destructive) neurological condition attributed to HIV infection, characterized by a group of clinical presentations including loss of coordination, mood swings, loss of inhibitions, and widespread inability to think. It is the most severe manifestation of HIV-associated neurocognitive disorder (HAND) and usually is seen in persons with untreated or inadequately treated late-stage HIV disease.
  • HIV-Exposed Infant An infant born to a mother infected with HIV and exposed to HIV during pregnancy, childbirth, or breast feeding.
  • Hodgkin disease A progressive cancer of the lymphatic system. Symptoms include lymphadenopathy, wasting, weakness, fever, itching, night sweats, and anemia. Treatment includes radiation and chemotherapy.
  • Home sample collection test A test kit that a consumer purchases and uses to collect blood (or other body fluid) to send away for testing.
  • Homosexual Pertaining to sexual activity with a person of the same sex.
  • Hormone An active chemical substance formed in one part of the body and carried in the blood to other parts of the body where it stimulates or suppresses cell and tissue activity.
  • Host factors The body's mechanisms for containing HIV, including immune system cells.
  • HTLV-1; HTLV-2 HTLV-I and HTLV-II, like all retroviruses, are single-stranded RNA that divide through DNA made possible by the presence of an enzyme, reverse transcriptase, which converts a single-stranded viral RNA into a double-stranded DNA. HTLV-I attacks T lymphocytes; it appears to be the causative agent of certain T- cell leukemias, T-cell lymphomas, and HTLV-I-associated neurologic disease.
  • Human immunodeficiency virus type 1 (HIV-1) HIV-1 and HIV-2 are retroviruses that cause the immune destruction of HIV disease and AIDS. HIV-1 is classified as a lentivirus in a subgroup of retroviruses. Retroviruses are single-stranded RNA that convert themselves into DNA through the action of an enzyme, reverse transcriptase. HIV inserts its DNA product into the host cell's DNA, preventing the host cell from carrying out its natural functions and turning it into an HIV factory. See Lentivirus; Retrovirus.
  • Human immunodeficiency virus type 2 (HIV-2) A virus closely related to HIV-1 that has also been found to cause AIDS. It was first isolated in West Africa. HIV-1 and HIV-2 differ in their geographic patterns of infection. HIV-1 remains the most common cause of AIDS and represents the major type distributed worldwide.
  • Human papillomavirus (HPV) HPV is transmitted through sexual contact and is the virus that causes genital warts and plays a causative role in cervical dysplasia and cervical cancer.
  • Hyperglycemia An abnormally high concentration of glucose (sugar) in the circulating blood, seen especially in patients with diabetes mellitus.
  • Hyperlipidemia An increase in the blood levels of triglycerides and cholesterol (fats) that can lead to heart disease and inflammation of the pancreas.
  • Hyperplasia Abnormal increase in the parts of tissue or cells.
  • Hypertriglyceridemia Elevated levels of triglycerides (fatty acid compounds) in the bloodstream. High levels contribute to heart disease.
  • Hypothesis An assumption as a basis for reasoning or argument, or as a guide to experimental investigation.
  • Hypoxia Reduction of oxygen supply to tissues.

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I[edit | edit source]

  • IDU Intravenous (injection) drug use.
  • Immune response The activity of the immune system against foreign substances.
  • Immune system The body's complicated natural defense against disruption caused by invading foreign agents (eg, bacteria, viruses). Acquired, or learned, immune response occurs when specialized cells (dendritic cells and macrophages) process pieces of infectious agents. The ultimate result is the creation of antibody-producing B cells and cytotoxic T lymphocytes.
  • Immune thrombocytopenic purpura (ITP) Also called idiopathic immune thrombocytopenic purpura. A condition in which the body produces antibodies against the platelets in the blood, which are cells responsible for blood clotting. ITP is very common in persons with HIV.
  • Immunity A natural or acquired resistance to a specific disease. Immunity may be partial or complete, long lasting or temporary.
  • Immunization Protection against an infectious disease by vaccination, usually with a weakened (attenuated) or killed form of the disease-causing microorganism. While people are usually immunized against an infectious disease by getting vaccinated, having a disease such as measles, mumps, or rubella one time usually prevents or "immunizes" a person from getting this disease again.
  • Immunocompetent Capable of developing an immune response; possessing a normal immune system.
  • Immunocompromised Refers to an immune system in which the ability to resist or fight infections and tumors is subnormal.
  • Immunodeficiency Breakdown of the immune system in which certain parts of the immune system no longer function. This condition makes a person more susceptible to certain diseases.
  • Immunogen (Antigen) A substance capable of provoking an immune response.
  • Immunogenicity The ability of an antigen or vaccine to stimulate an immune response.
  • Immunoglobulin (Ig) Also called immune serum globulin. A class of proteins also known as antibodies made by the B cells of the immune system in response to a specific antigen. There are five classes of immunoglobulins.
  • Immunoglobulin A (IgA) A class of antibodies that is secreted into bodily fluids such as saliva. IgA protects the body's mucosal surfaces from infections.
  • Immunoglobulin G (IgG) The dominant class of antibodies and the one that provides long-term protection against infection. During pregnancy, IgG crosses the placenta to the fetus and protects it against infection. Also called gammaglobulin.
  • Immunoglobulin M (IgM) A class of antibodies that is made by the body as the initial response to an infection or immunization. If IgM is made in response to an immunization, a booster shot will result in a "switch" from IgM to mostly immunoglobulin G.
  • Immunostimulant Any agent or substance that triggers or enhances the body's defense; also called immunopotentiator.
  • Immunosuppression A state of the body in which the immune system is damaged and does not perform its normal functions. Immunosuppression may be induced by drugs (e.g., in chemotherapy) or result from certain disease processes, such as HIV infection.
  • Immunotherapy Treatment aimed at restoring an impaired immune system.
  • Immunotoxin A plant or animal toxin (ie, poison) that is attached to an antibody and used to destroy a specific target cell.
  • In utero Before birth; literally, in the uterus.
  • In vitro An artificial environment created outside a living organism (eg, a test tube or culture plate) used in experimental research to study a disease or process.
  • In vivo ("In life") Within living organisms. (Often refers to animal or human studies.)
  • Incidence The number of new cases (e.g., of a disease) occurring in a given population over a certain period of time. Also called seroincidence.
  • Inclusion/Exclusion criteria The medical or social standards determining whether a person may or may not be allowed to enter a clinical trial. For example, some trials may not allow persons with chronic liver disease or with certain drug allergies; others may exclude men or women, or include only persons with a lowered T-cell count.
  • Incubation period The time interval between the initial infection with an infectious agent (e.g., HIV) and the appearance of the first symptom or sign of disease.
  • Indeterminate test result A laboratory test result that does not provide a clear answer. Either additional laboratory studies should be performed or the test should be repeated.
  • Infection The state or condition in which the body (or part of the body) is invaded by an infectious agent (eg, a bacterium, fungus, or virus) that multiplies and produces an injurious effect (active infection). As related to HIV, infection typically begins when HIV encounters a CD4+ cell.
  • Infectious An infection capable of being transmitted by direct or intimate contact (e.g., sex).
  • Informed consent A process during which the patient learns the key facts about HIV testing--including what will occur during HIV testing and counseling and the purpose and benefits of HIV testing--before deciding whether to allow testing to proceed.
  • Infusion The process of administering fluid, other than blood, to an individual by slowly injecting a solution of the compound into a vein. Infusions are often used when the drug is too toxic or the volume is too large to be given by quick injection.
  • Inoculation The introduction of a substance (inoculum; e.g., a vaccine, serum, or virus) into the body to produce or increase immunity to the disease or condition associated with the substance. See Vaccine.
  • Institutional review board (IRB) A committee of physicians, statisticians, researchers, community advocates, and others that ensures that a clinical trial is ethical and that the rights of study participants are protected.
  • Insulin resistance A condition in which the body is unable to respond to and use the insulin it produces. As a result, the pancreas secretes more insulin into the bloodstream in an effort to reduce blood glucose levels.
  • Integrase An enzyme that inserts HIV's genes into a cell's normal DNA. It plays a vital role in the HIV infection process.
  • Integrase inhibitors A class of anti-HIV drugs that prevents the HIV integrase enzyme from inserting viral DNA into a host cell's normal DNA.
  • Intent to treat Analysis of clinical trial results that includes all data from patients in the groups to which they were randomized (ie, assigned through random distribution) even if they never received the treatment.
  • Interferon One of a number of antiviral proteins that control the immune response. Interferon (IFN) alpha is secreted by a virally infected cell and strengthens the defenses of nearby uninfected cells. A manufactured version of IFN alpha is an FDA-approved treatment for certain conditions. Interferon gamma is synthesized by immune system cells (natural killer cells and CD4 cells). It activates macrophages and helps promote cellular immunity.
  • Interleukins Substances (cytokines) that are released from immune and other cells. There are many types referred to as interleukin (IL) 1, 2, 3, 4, 5, etc.
  • Interstitial Relating to or situated in the small, narrow spaces between tissues or parts of an organ.
  • Intervention An action or strategy to change a particular problem or outcome or accomplish a specific result (e.g., use of ART to prevent HIV disease progression).
  • Intravenous (IV) Of, or pertaining to, the inside of a vein. An injection made directly into a vein.
  • Intravenous immunoglobulin (IVIG) A sterile solution of concentrated antibodies extracted from healthy people. IVIG may be used to prevent certain infections in persons with low or abnormal antibody production. IVIG is injected into a vein.
  • Isolate An individual part of an organism (such as a spore, bacteria or virus) that has been separated (as from diseased tissue, contaminated water, or the air) from the whole.
  • Isoniazid (INH) An orally administered drug used to eliminate tuberculosis infection in people without active disease. INH is also administered in combination with other drugs to treat active tuberculosis

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  • Jaundice Yellow pigmentation of the skin, mucous membranes, whites of the eyes, and body fluids caused by elevated blood levels of bilirubin. The condition is associated with either liver or gallbladder disease or excessive destruction of red blood cells.
  • Kaposi sarcoma (KS) An AIDS-defining illness consisting of individual cancerous sores 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 mouth. KS also can occur internally, especially in the intestines, lymph nodes, and lungs, and in such cases, is life threatening. A species of herpes virus--also referred to as Kaposi sarcoma herpes virus (KSHV) or HHV-8--similar to the Epstein-Barr virus is the probable cause.
  • Karnofsky score A score from 0 to 100 assigned by a physician based on observations of a patient's ability to perform common tasks. Thus, 100 signifies normal physical abilities with no evidence of disease. Decreasing numbers indicate a reduced ability to perform activities of daily living.
  • Killer T cells Because viruses lurk inside host (e.g., human) cells where antibodies cannot reach them, the only way to eliminate them is by killing the infected host cell. To do this, the immune system uses a kind of white blood cell, called the killer T cell. Also known as cytotoxic T cells (or cytotoxic T lymphocytes). See Natural killer (NK) cells; T cells.

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  • Lactic acidosis A buildup of lactic acid in the blood, accompanied by low blood pH. This is a potentially fatal condition characterized by nausea, abdominal pain, fatigue, muscle weakness, and shortness of breath. Also referred to as lactic acidemia.
  • Latency The period when an infecting organism is in the body but is not producing any clinically noticeable ill effects or symptoms. In HIV disease, clinical latency is an asymptomatic period in the early years of HIV infection. The period of latency is characterized by near-normal CD4+ T-cell counts. Recent research indicates that HIV remains quite active in the lymph nodes during this period.
  • Lentivirus "Slow" virus characterized by a long time frame between infection and the onset of symptoms. HIV is a lentivirus, as is the simian immunodeficiency virus (SIV) that infects nonhuman primates.
  • Lesion A general term to describe an area of altered tissue (e.g., the infected patch or sore in a skin disease).
  • Leukocytes Any of the various white blood cells that together make up the immune system. Neutrophils, lymphocytes, and monocytes are all leukocytes.
  • Leukocytosis An abnormally high number of leukocytes in the blood. This condition can occur during many types of infection and inflammation.
  • Leukopenia A decrease in the number of white blood cells. The threshold value for leukopenia usually is taken as <5,000 white blood cells per cubic millimeter of blood.
  • Lipid Any of a group of fats and fatlike compounds, including sterols, fatty acids, and many other substances.
  • Lipodystrophy Abnormal body fat distribution, either loss of subcutaneous fat (lipoatrophy) or accumulation of visceral fat (lipohypertrophy); both may occur in the same person. In HIV, lipodystrophy may be related to advanced disease, with older antiretroviral medications, or other factors. It has become much less common in recent years.
  • Live vector vaccine As pertaining to HIV, a vaccine that uses an attenuated (i.e., weakened) virus or bacterium to carry pieces of HIV into the body to directly stimulate a cell-mediated immune response.
  • Liver function test (LFT) A test that measures the blood serum level of any of several enzymes (e.g., AST and ALT) produced by the liver. An elevated liver function test result is a sign of possible liver damage.
  • Long-term nonprogressors Individuals who have been living with HIV for at least 7 to 12 years (different authors use different time spans) and have stable CD4+ T-cell counts of 500 or more cells per cubic millimeter of blood, no HIV-related diseases, and no previous antiretroviral therapy. Data suggest that this phenomenon is associated with the maintenance of the integrity of the lymphoid tissues and with less virus trapping in the lymph nodes than is seen in other individuals living with HIV.
  • Lumbar puncture A procedure in which cerebrospinal fluid from the subarachnoid space in the lumbar region is removed for examination. Also known as spinal tap.
  • Lymph A transparent, slightly yellow fluid that carries lymphocytes. Lymph is derived from tissue fluids collected from all parts of the body and is returned to the blood via lymphatic vessels.
  • Lymph nodes Small, bean-sized organs of the immune system, distributed widely throughout the body. Lymph fluid is filtered through the lymph nodes in which all types of lymphocytes take up temporary residence. Lymph nodes contain T cells, B cells, as well as other cells of the immune system.
  • Lymphoid interstitial pneumonitis (LIP) A type of pneumonia that affects 35% to 40% of children with AIDS, and which causes hardening of the lung membranes involved in absorbing oxygen. LIP is an AIDS-defining illness in children. The cause of LIP is not clear. There is no established treatment for LIP, but the use of corticosteroids for progressive LIP has been advocated.
  • Lymphoid organs Include tonsils, adenoids, lymph nodes, spleen, thymus, and other tissues. These organs act as the body's filtering system, trapping any invading foreign particles (e.g., bacteria and viruses) and presenting them to squadrons of immune cells that congregate there.
  • Lymphoma Cancer of the lymphoid tissues. Lymphomas are often described as being large-cell or small-cell types, cleaved or noncleaved, or diffuse or nodular. The different types often have different prognoses (i.e., prospect of survival or recovery). Lymphomas can be referred to by the organs in which they are active, such as CNS lymphomas, which are in the central nervous system, and GI lymphomas, which are in the gastrointestinal tract. The types of lymphomas most commonly associated with HIV infection are called non-Hodgkin lymphomas or B-cell lymphomas. In these types of cancers, certain cells of the lymphatic system grow abnormally. They divide rapidly, growing into tumors.
  • Lymphopenia A relative or absolute reduction in the number of lymphocytes in the circulating blood.
  • Lysis Rupture and destruction of a cell.

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  • Macrophage A large immune cell that destroys invading infectious agents. Macrophages can hide large quantities of HIV without being killed, acting as reservoirs of the virus.
  • Macrophage-tropic virus HIV strains that infect macrophages. They readily fuse with cells that have both CD4 and CCR5 molecules on their surfaces, whereas the same viral isolates fail to fuse with cells expressing only CD4. These isolates are the main ones found in patients during the symptom-free stage of HIV disease.
  • Magnetic resonance imaging (MRI) A noninvasive, non-x-ray diagnostic technique that provides computer-generated images of the body's internal tissues and organs.
  • Maintenance therapy Also referred to as secondary prophylaxis. A therapy that prevents reoccurrence of an infection that has been brought under control.
  • Malaise A generalized, nonspecific feeling of discomfort or tiredness.
  • Malaria An infectious disease characterized by cycles of chills, fever, and sweating, caused by a parasite transmitted by a host mosquito.
  • Malignant Refers to cells or tumors growing in an uncontrolled fashion. Such growths may spread to and disrupt nearby normal tissue, or reach distant sites via the bloodstream. By definition, cancers are always malignant, and the term "malignancy" implies cancer. See Metastasis.
  • Mast cell A granulocyte found in tissue. The contents of the mast cells, along with those of basophils, are responsible for the symptoms of allergy.
  • Memory T cells A subset of T lymphocytes that have been exposed to specific antigens and can then proliferate (i.e., reproduce) on subsequent immune system encounters with the same antigen.
  • Meninges Membranes surrounding the brain or spinal cord. Part of the so-called blood-brain barrier. See Meningitis.
  • Meta-Analysis A quantitative method of combining the results of independent studies (usually drawn from the published literature) and synthesizing summaries and conclusions.
  • Metabolism The chemical changes in living cells by which energy is provided for vital processes and activities and new material is assimilated.
  • Metastasis The spread of a disease (e.g., cancer) from an original site to other sites in the body.
  • Microbes Microscopic living organisms, including bacteria, protozoa, viruses, and fungi.
  • Microbicide An agent (e.g., a chemical or antibiotic) that destroys microbes. In the field of HIV, may refer to rectal or vaginal compound given to prevent the transmission of HIV.
  • Micronutrients Vitamins or minerals that are necessary to maintain health and that the body must obtain from outside sources.
  • Microsporidiosis An intestinal infection that causes diarrhea and wasting in persons with HIV. It results from two species of microsporidia, a protozoal parasite. In HIV infection, it generally occurs when CD4+ T-cell counts fall below 100. See Wasting syndrome; Pathogen; Protozoa.
  • Mitochondria A rod-shaped or oval portion on the inside of a cell that produces most of the cell's energy.
  • Mitochondrial toxicity Also referred to as mitochondrial dysfunction. A possible side effect of certain anti-HIV drugs, primarily early NRTIs such as zidovudine and stavudine, that results in mitochondrial damage. This damage can cause symptoms in the heart, nerves, muscles, pancreas, kidney, and liver, and it also can cause changes in lab tests. Some of the common conditions related to mitochondrial toxicity are muscle and nerve disease and inflammation of the pancreas.
  • Molluscum contagiosum A disease of the skin and mucous membranes caused by a poxvirus (molluscum contagiosum virus, MCV) infection. It is characterized by pearly white or flesh-colored papules (bumps) on the face, neck, and genital region. In persons living with HIV, molluscum contagiosum often is a progressive disease, resistant to treatment. When CD4+ cell counts fall below 200, the lesions tend to proliferate and spread.
  • Monocyte A large white blood cell that ingests infectious agents or other cells and foreign particles. When a monocyte enters tissues, it develops into a macrophage.
  • Monotherapy Use of a single drug or therapy to treat a disease or condition.
  • Morbidity The condition of being diseased or sick; also the incidence of disease or rate of sickness.
  • MSM Men who have sex with men; a term created to include those who do not identify as gay or bisexual.
  • MTCT Mother-to-child transmission (of HIV).
  • Mucocutaneous Anything that concerns or pertains to mucous membranes and the skin (e.g., mouth, eyes, vagina, lips, or anal area).
  • Mucosal immunity Resistance to infection across the mucous membranes. Dependent on immune cells and antibodies present in the lining of the urogenital tract, gastrointestinal tract, and other parts of the body exposed to the outside world.
  • Mucous membrane Moist layer of tissue lining the digestive, respiratory, urinary, and reproductive tracts--all the body cavities with openings to the outside world except the ears.
  • Mutation In biology, a sudden change in a gene or unit of hereditary material that results in a new inheritable characteristic. As related to HIV: During the course of HIV disease, mutated HIV strains may emerge in an infected individual. These mutated strains may differ widely in their ability to infect and kill different cell types, as well as in their rate of replication. Of course, HIV does not mutate into another type of virus.
  • Myalgia Muscle pain or tenderness, sometimes accompanied by malaise (vague feeling of discomfort or weakness).
  • Mycobacterium Any bacterium of the genus Mycobacterium or a closely related genus.
  • Mycobacterium avium complex (MAC) A common opportunistic infection caused by two very similar mycobacterial organisms, Mycobacterium avium and Mycobacterium intracellulare (MAI), found in soil and dust particles. The infection that can be localized (limited to a specific organ or area of the body) or disseminated throughout the body. MAC disease is extremely rare in persons who are not infected with HIV. It generally occurs when the CD4+ T-cell count falls below 50 and the person is not on antiretroviral therapy or prophylaxis.
  • Mycosis Any disease caused by a fungus.
  • Myelosuppression Suppression of bone marrow activity, causing decreased production of red blood cells (anemia), white blood cells (leukopenia), or platelets (thrombocytopenia). Myelosuppression is a side effect of some drugs, such as AZT.
  • Myopathy Progressive muscle weakness. Myopathy may arise as a toxic reaction to AZT or as a consequence of the HIV infection itself.

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N[edit | edit source]

  • Nadir The lowest point. For example, a patient's CD4 nadir is that person's lowest measured CD4 count.
  • National Institutes of Health (NIH) In the United States, a multi-institute agency of the U.S. Department of Health and Human Services. NIH is the federal focal point for health research. It conducts research in its own laboratories and supports research in universities, medical schools, hospitals, and research institutions throughout the United States and abroad. Internet address: http://www.nih.gov/
  • Natural history study Study of the natural development of something (such as an organism or a disease) over a period of time.
  • Neonatal Concerning the first 6 weeks of life after birth.
  • Neoplasm An abnormal and uncontrolled growth of tissue; a tumor.
  • Neuralgia A sharp, shooting pain along a nerve pathway.
  • Neuropathy The name given to a group of disorders involving nerves. Symptoms range from a tingling sensation or numbness in the toes and fingers to paralysis. See Peripheral neuropathy.
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  • Neutralization The process by which an antibody binds to specific antigens, thereby "neutralizing" the microorganism.
  • Neutralizing antibody An antibody that keeps a virus from infecting a cell, usually by blocking receptors on the cell or the virus.
  • Neutropenia An abnormal decrease in the number of neutrophils (the most common type of white blood cell) in the blood. The decrease may be relative or absolute. Neutropenia may be associated with HIV infection or may be drug induced.
  • Neutrophil A type of white blood cell (leukocyte) that engulfs and kills foreign microorganisms such as bacteria.
  • Non-Hodgkin lymphoma (NHL) A lymphoma made up of B cells and characterized by nodular or diffuse tumors that may appear in the stomach, liver, brain, and bone marrow of persons with HIV. After Kaposi sarcoma, NHL is the most common opportunistic cancer in persons with AIDS.
  • NSAID A classification of drugs called nonsteroidal antiinflammatory drugs. NSAIDs reduce inflammation and are used to treat arthritis and mild-to-moderate pain.
  • Nucleic acid test A technology that allows detection of very small amounts of genetic material (DNA or RNA) in blood, plasma, and tissue. A nucleic acid test can detect any number of viruses in blood or blood products, thereby better assuring the safety of the blood supply.
  • Nucleoside A building block of nucleic acids, DNA, or RNA, the genetic material found in living organisms. Nucleosides are nucleotides without the phosphate groups.
  • Nucleoside analogue An artificial copy of a nucleoside. When incorporated into the DNA or RNA of a virus during viral growth, the nucleoside analogue acts to prevent production of new virus.
  • Nucleoside reverse transcriptase inhibitor (NRTI) A nucleoside analogue antiretroviral drug whose chemical structure constitutes a modified version of a natural nucleoside. These compounds suppress replication of retroviruses by interfering with the reverse transcriptase enzyme. The nucleoside analogues cause premature termination of the proviral (viral precursor) DNA chain.
  • Nucleotide Nucleotides are the building blocks of nucleic acids, DNA, and RNA. Nucleotides are composed of phosphate groups, a five-sided sugar molecule (ribose sugars in RNA, deoxyribose sugars in DNA), and nitrogen-containing bases.
  • Nucleotide analogue Nucleotide analogues are drugs that are structurally related to nucleotides; they are chemically altered to inhibit production or activity of disease-causing proteins.
  • Nucleus The central controlling body within a living cell, usually a spherical unit enclosed in a membrane and containing genetic codes for maintaining the life systems of the organism and for issuing commands for growth and reproduction.

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  • Occupational HIV exposure Exposure to HIV as a result of work (job) activities. Exposure may include accidental exposure to HIV-infected blood following a needlestick injury or cut from a surgical instrument.
  • Oncology The branch of medicine that studies cancers or other tumors.
  • Opportunistic infection An illness 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 jiroveci pneumonia; Kaposi sarcoma; cryptosporidiosis; histoplasmosis; other parasitic, viral, and fungal infections; and some types of cancer.
  • Opt in In HIV testing, a procedure whereby an individual is counseled about HIV and is given the option of accepting or rejecting an HIV test. They "opt in" when they agree to have the tested done.
  • Opt out In HIV testing, a procedure whereby an individual is counseled about HIV and is only given the option of refusing an HIV test. If they refuse the test they have "opted out" of HIV testing. Studies have shown that more individuals agree to HIV testing when an opt out approach is used.
  • OPV Oral polio vaccine.
  • Oral fluid test A test using oral mucosal fluid. To differentiate this fluid from saliva, an absorbent material is left in the mouth for several minutes. In a person with HIV, oral mucosal fluid is likely to contain HIV antibodies.
  • Oral hairy leukoplakia (OHL) A whitish lesion that appears on the side of the tongue and inside the cheeks. The lesion appears raised, with a ribbed or hairy surface. OHL occurs mainly in persons with declining immunity and may be caused by Epstein-Barr virus infection. OHL was not observed before the HIV epidemic.
  • Oral sex A type of sexual intercourse in which a partner's genitals are stimulated by mouth and tongue.
  • Oropharyngeal Relating to the division of the pharynx between the soft palate and the epiglottis. The pharynx is a tube that connects the mouth and nasal passages with the esophagus, the connection to the stomach. The epiglottis is a thin, valvelike structure that covers the glottis, the opening of the upper part of the larynx (the part of the throat containing the vocal cords), during swallowing.
  • Otitis Inflammation of the ear, which may be marked by pain, fever, abnormalities of hearing, hearing loss, tinnitus, and vertigo.
  • Otitis media Infection and inflammation of the middle ear space and eardrum.

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P-Q[edit | edit source]

  • P24 antigen A bullet-shaped part of a protein that surrounds the viral RNA within the envelope of HIV. The p24 antigen test (which is included in the fourth-generation Ag/Ab HIV test) looks for the presence of this protein in a patient's blood. A positive result for the p24 antigen suggests active HIV multiplication.
  • Package insert A document, approved by the FDA and furnished by the manufacturer of a drug (inserted into the package), for use when dispensing the drug. The document indicates approved uses, contraindications, and potential side effects.
  • Palliative A treatment that provides symptomatic relief but not a cure.
  • Palliative care Palliative care is an approach to life-threatening chronic illnesses, especially at the end of life. Palliative care combines active and compassionate therapies to comfort and support patients who are living with life-ending illnesses and their families. Palliative care strives to meet physical needs through relieving pain and maintaining quality of life while emphasizing the patient's and family's rights to participate in informed discussions and to make choices. This patient- and family-centered approach uses the skills of interdisciplinary team members to provide a comprehensive continuum of care, including spiritual and emotional needs.
  • Pandemic A disease prevalent throughout an entire country or continent, or the whole world. See Epidemic.
  • Pap smear A method for the early detection of cancer and other abnormalities of the anogenital tract, especially of the cervix and anus.
  • Parasite A plant or animal that lives and feeds on or within another living organism (host), causing some degree of harm to the host organism.
  • Parenteral A route other than in or through the digestive system. For example, parenteral can pertain to blood being drawn from a vein in the arm or introduced into that vein via a transfusion (intravenous), or to injection of medications or vaccines through the skin (subcutaneous) or into muscle (intramuscular).
  • Paresthesia Abnormal sensations such as burning, tingling, or a "pins-and-needles" feeling. Paresthesia may constitute the first group of symptoms of nerve involvement in HIV infection.
  • Pathogen Any disease-producing microorganism or material.
  • Pelvic inflammatory disease (PID) Gynecological condition caused by an infection (usually sexually transmitted) that spreads from the vagina to the upper parts of a woman's reproductive tract in the pelvic cavity. PID takes different courses in different women, but can cause abscesses and constant pain almost anywhere in the genital tract. If left untreated, it can cause infertility or more frequent periods.
  • Perinatal Pertaining to or occurring in the period shortly before and after birth, variously defined as beginning with completion of the 20th to 28th week of gestation and ending 7 to 28 days after birth.
  • Perinatal transmission Transmission of a pathogen, such as HIV, from mother to baby before, during, or after the birth process.
  • Peripheral neuritis Inflammation of far portion of the nerves or the nerve endings, usually associated with pain, muscle wasting, and loss of reflexes.
  • Peripheral neuropathy Condition characterized by sensory loss and often pain in the hands or legs and feet. It may start with burning or tingling sensations or numbness in the toes and fingers. In severe cases, muscle weaknesss may be present. Peripheral neuropathy may arise from an HIV-related condition or be the side effect of certain drugs, some of the older nucleoside analogues in particular.
  • Persistent generalized lymphadenopathy (PGL) Chronic, diffuse, noncancerous lymph node enlargement. Typically it has been found in persons with persistent bacterial, viral, or fungal infections. PGL in HIV infection is a condition in which lymph nodes are chronically swollen in at least two areas of the body for 3 months or more with no obvious cause other than the HIV infection.
  • Phagocyte A cell that is able to ingest and destroy foreign matter, including bacteria.
  • Pharmacokinetics The processes (in a living organism) of absorption, distribution, metabolism, and excretion of a drug or vaccine.
  • Phenotype The genetic makeup of an organism such as HIV as it interacts with the environment. In the case of HIV, the virus may interact with cells and drugs. Phenotypic resistance testing determines whether an organism is susceptible to a specific drug in a test tube. Contrast with genotype.
  • Placebo A substance that has no activity, often used in a clinical study so that participants do no know if they are receiving the active (study drug) or the inactive placebo. This approach assists in performing clinical studies and determining whether a drug is active against a disease.
  • Placebo effect A physical or emotional change, occurring after a substance is taken or administered, that is not the result of any special property of the substance. The change may be beneficial, reflecting the expectations of the patient and, often, the expectations of the person giving the substance.
  • Placebo-controlled study A method of investigation of drugs in which an inactive substance (placebo) is given to one group of patients, while the drug being tested is given to another group. The results obtained in the two groups are then compared to see if the investigational treatment is more effective in treating the condition.
  • Plasma The liquid part of the blood and lymph that contains nutrients, electrolytes (dissolved salts), gases, albumin, clotting factors, wastes, and hormones.
  • Platelets Active agents of inflammation that are released when damage occurs to a blood vessel. The platelets stick to the blood vessel walls, forming clots to prevent the loss of blood. Some persons living with HIV develop thrombocytopenia, a condition characterized by a platelet count of <100,000 platelets per cubic millimeter of blood.
  • PLHA People living with HIV/AIDS.
  • PLWHA People living with HIV/AIDS.
  • PMTCT Prevention of mother-to-child transmission (of HIV).
  • Pneumocystis jiroveci pneumonia (PCP, PJP) An infection of the lungs caused by Pneumocystis jiroveci, which is thought to be a protozoan but may be more closely related to a fungus. P jiroveci grows rapidly in the lungs of persons with AIDS and is a frequent AIDS-related cause of death. P jiroveci infection sometimes may occur elsewhere in the body (skin, eye, spleen, liver, or heart).
  • Polymerase chain reaction (PCR) A laboratory process in which a DNA segment is selected from a mixture of DNA chains and rapidly multiplies to create a large sample of a piece of DNA. It is a sensitive laboratory technique that can detect and measure HIV in a person's blood or lymph nodes (also called RT-PCR). It also is a means of measuring the amount of virus in the blood (viral load).
  • Positive test result Any result that indicates that a person has a disease or infection. For HIV, a positive test result indicates that the person has been infected with HIV.
  • Postexposure prophylaxis (PEP) As it relates to HIV disease, a potentially preventative treatment using antiretroviral drugs to treat individuals within 72 hours of a high-risk exposure (e.g., needlestick injury, unprotected sex, needle sharing) to prevent HIV infection.
  • Postnatal Occurring after birth, especially during the period immediately after birth.
  • Preconception counseling Recommended for all women of childbearing age as a component of their primary medical care. The purpose of preconception care is to identify risk factors for adverse maternal or fetal outcome, provide education and counseling targeted to the patient's individual needs, and treat or stabilize medical conditions prior to conception in order to optimize maternal and fetal outcomes.
  • Preexposure prophylaxis (PrEP) In reference to HIV, a medication given before exposure to HIV in order to prevent infection. The PrEP medications are Truvada and Descovy.
  • Prenatal The period preceding birth, during which the fetus develops in the uterus.
  • Prevalence A measure of the proportion of people in a population affected with a particular disease at a given time.
  • Primary isolate HIV taken from an infected individual (as opposed to being grown in laboratory cultures).
  • Probability The chance, or likelihood, that a certain event will occur.
  • Prodrome A symptom that indicates the onset of a disease.
  • Progressive multifocal leukoencephalopathy (PML) A rapidly debilitating opportunistic infection caused by the JC virus that infects brain tissue and causes damage to the brain and the spinal cord. Symptoms vary from patient to patient but include loss of muscle control, paralysis, blindness, problems with speech, and an altered mental state. PML can lead to coma and death.
  • Prophylaxis Treatment to prevent the onset of a particular disease (primary prophylaxis), or the recurrence of symptoms in an existing infection that has been brought under control (secondary prophylaxis, maintenance therapy).
  • Protease An enzyme that breaks down proteins into their component peptides. HIV's protease enzyme breaks apart long strands of viral protein into the separate proteins making up the viral core. The enzyme acts as new virus particles are budding off a cell membrane. Protease is the first HIV protein for which a three-dimensional structure has been characterized.
  • Protease inhibitor A class of antiviral drugs that act by inhibiting the virus' protease enzyme, thereby preventing viral replication. Specifically, these drugs block the protease enzyme from breaking apart long strands of viral proteins to make the smaller, active HIV proteins that comprise the virion. If the larger HIV proteins are not broken apart, they cannot assemble themselves into new functional HIV particles.
  • Protocol The detailed plan for conducting clinical studies. It states the trial's rationale, purpose, drug or vaccine dosages, length of study, routes of administration, who may participate (Inclusion/Exclusion Criteria), and other aspects of trial design. See Inclusion/Exclusion criteria.
  • Purified protein derivative (PPD) Material used in the tuberculin skin test (TST); a common test for exposure to Mycobacterium tuberculosise bacterium that causes tuberculosis (TB). PPD is sometimes used synonymously with TST. In the PPD test, a small amount of protein from TB is injected under the skin. If patients have been previously infected, they will mount a delayed-type hypersensitivity reaction, characterized by a hard, red bump called an induration.
  • PWID A person who injects drugs. People who inject drugs.  
  • QD Once each day.
  • QID Four times each day.

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R[edit | edit source]

  • Rapid HIV test A screening test for detecting antibody to HIV that produces very quick results, usually in 5 to 30 minutes. For diagnosis of HIV infection, a positive rapid test is confirmed with a second rapid test made by a different manufacturer.
  • Reagent A substance used in a chemical reaction to detect, analyze, or produce another substance.
  • Rebound An increase in viral load following a previous decrease due to anti-HIV therapy.
  • Receptor A molecule on the surface of a cell that serves as a recognition or binding site for antigens, antibodies, or other cellular or immunological components.
  • Referral A suggestion that a patient see another individual (usually a specialist) for another opinion.
  • Refractory Referring to a disease that does not readily respond to treatment.
  • Reinfection/Superinfection The infection of an already HIV-infected person with another strain of HIV. The superinfection can be with a more aggressive strain of HIV.
  • Remission The lessening in the severity of symptoms or duration of an outbreak of a disease.
  • Resistance Reduction in a microorganism's sensitivity to a particular drug. Resistance is thought to result usually from a genetic mutation. In HIV, such mutations can change the structure of viral enzymes and proteins so that an antiviral drug can no longer bind with them as well as it used to.
  • Resistance Testing The evaluation of bacteria or viruses such as HIV to determine whether they are resistant to the effects of drugs used for treatment. Resistance testing is an important tool to determine whether a patient with HIV infection is getting sicker because ARV drugs are no longer working. See Genotype; Phenotype.
  • Retina Light-sensitive tissue at the back of the eye that transmits visual impulses to the brain via the optic nerve. See Retinitis.
  • Retinal detachment Condition in which a portion of the retina becomes separated from the inner wall of the eye. In AIDS patients, it can result from retinal disease such as cytomegalovirus (CMV) retinitis.
  • Retinitis Inflammation of the retina, linked in AIDS to cytomegalovirus (CMV) infection. Untreated, it can lead to blindness.
  • 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.
  • Reverse transcriptase An enzyme capable of copying RNA into DNA during the HIV multiplication cycle. Several anti-HIV drugs--such as AZT, ddI, and ddC--are chemicals that act against the reverse transcriptase enzyme.
  • Ribonucleic Acid (RNA) A nucleic acid, found mostly in the cytoplasm of cells (rather than in the nucleus) that is important in the synthesis of proteins.
  • Risk Assessment Risk assessment is a fundamental part of an HIV prevention counseling session in which the individual is encouraged to identify, acknowledge, and discuss in detail his or her personal risk for acquiring or transmitting HIV.

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S[edit | edit source]

  • Salmonella A family of gram-negative bacteria, found in undercooked poultry or eggs, that are a common cause of food poisoning. Salmonella infection can be more severe in people with HIV.
  • Salvage therapy Also referred to as rescue therapy. A treatment effort for people whose antiretroviral regimens have failed at least two times and who have had extensive prior exposure to antiretroviral agents.
  • Sarcoma A malignant (cancerous) tumor of the skin and soft tissue.
  • Seborrheic dermatitis A chronic inflammatory disease of the skin of unknown cause or origin, characterized by moderate redness; dry, moist, or greasy scaling; and yellow crusted patches on various areas, including the mid-parts of the face, ears, above the orbit of the eye, umbilicus (the navel), genitalia, and especially the scalp.
  • Sensitivity (of a test) The sensitivity of a test is the probability of it giving a positive result if infection is truly present. As the sensitivity of the test increases the proportion of false negatives decreases.
  • Sepsis The presence of harmful microorganisms or associated toxins in the blood.
  • Seroconversion The development of antibodies to a particular bacteria, virus, or vaccine. When people develop antibodies to HIV, they seroconvert from antibody negative to antibody positive. It may take from as little as 1 week to several months or more after infection with HIV for antibodies to the virus to develop. After antibodies to HIV appear in the blood, a person should test positive on antibody tests. See Incubation period; Window period.
  • Seroincidence The rate of new infections within a specific target population within a given period of time.
  • Serologic test Any number of tests that are performed on the clear fluid portion of blood. Often refers to a test that determines the presence of antibodies to antigens such as viruses.
  • Seroprevalence As related to HIV infection, the proportion of persons who have serologic (i.e., pertaining to serum) evidence of HIV infection at any given time.
  • Serostatus Results of a blood test for specific antibodies.
  • Serum The clear, thin, and sticky fluid portion of the blood that remains after coagulation (clotting). Serum contains no blood cells, platelets, or fibrinogen.
  • Set point The measurable holding point or balance between the virus and the body's immune system reported as the viral load measurement. The viral set point is established within a few weeks to a few months after infection and is thought to remain steady for an indefinite period of time. Set points are thought to determine how long it will take for disease progression to occur.
  • Sexually transmitted disease (STD) Also called venereal disease (VD) (an older public health term) or sexually transmitted infection (STI). STDs are infections spread by the transfer of organisms from person to person during sexual contact. In addition to the "traditional" STDs (syphilis and gonorrhea), the spectrum of STDs now includes HIV infection; Chlamydia trachomatis infections; human papillomavirus (HPV) infection; genital herpes; chancroid; genital mycoplasmas; hepatitis B; trichomoniasis; enteric infections; and ectoparasitic diseases (i.e., diseases caused by organisms that live on the outside the host's body). The complexity and scope of STDs have increased dramatically since the 1980s; more than 20 microorganisms and syndromes are now recognized as belonging in this category.
  • SGOT (Serum glutamic oxaloacetic transaminase) Also known as AST (aspartate aminotransaminase), a liver enzyme that plays a role in protein metabolism. Elevated serum levels of SGOT are a sign of liver damage from disease or drugs.
  • SGPT (Serum glutamic pyruvate transaminase) Also known as ALT (alanine aminotransaminase), a liver enzyme that plays a role in protein metabolism similar to that of SGOT. Elevated serum levels of SGPT are a sign of liver damage from disease or drugs.
  • Side effects The actions or effects of a drug (or vaccine) other than those desired. The term usually refers to undesired or negative effects, such as headache, skin irritation, or liver damage. Experimental drugs must be evaluated for both immediate and long-term side effects.
  • Sinusitis Inflammation of the nasal cavity and sinuses.
  • Specificity (of a test) The specificity of a test is the probability of the test providing a negative result if the disease is truly absent. As the specificity of a test increases, the proportion of false positives decreases.
  • Sputum Mucus and other matter that is brought up from the lungs by coughing.
  • Sputum analysis Method of detecting certain infections (especially tuberculosis) by culturing of sputum--the mucus matter that collects in the respiratory and upper digestive passages and is expelled by coughing.
  • Standards of care Treatment regimen or medical management based on state-of-the-art patient care.
  • Staphylococcus Type of bacteria that may cause various types of infection.
  • Stem cells Cells from which all blood cells derive. Bone marrow is rich in stem cells.
  • Stevens-Johnson syndrome A severe and sometimes fatal form of erythema multiforme that is characterized by severe skin manifestations; conjunctivitis (eye inflammation), which often results in blindness; Vincent angina (trench mouth); and ulceration of the genitals and anus.
  • Stomatitis Inflammatory diseases of the mouth (e.g. canker sores, thrush, fever blisters) having various causes, such as mechanical trauma, irritants, allergy, vitamin deficiency, or infection.
  • Strain Subgroup of a species. For HIV, different types of HIV such as HIV-1, HIV-2, clade A, clade B, etc.
  • Study endpoint A primary or secondary outcome used to judge the effectiveness of a treatment.
  • Subclinical infection An infection, or phase of infection, without readily apparent symptoms or signs of disease.
  • Subcutaneous (SQ) Beneath the skin or introduced beneath the skin (e.g., subcutaneous injections).
  • Sulfa drug A sulfonamide drug used to treat bacterial infections. These drugs inhibit the action of p-aminobenzoic acid, a substance bacteria need in order to reproduce.
  • Suppressor T cells (T8, CD8) Subset of T cells that halts antibody production and other immune responses.
  • Surrogate markers Variables (measures) that are followed in clinical trials when the variable of interest cannot be conveniently observed in a direct manner. Two commonly used surrogate markers in HIV studies are CD4+ T-cell counts and quantitative plasma HIV RNA (viral load).
  • Susceptible Vulnerable or predisposed to a disease or infection.
  • Symptoms Any perceptible, subjective change in the body or its functions that indicates disease or phases of disease, as reported by the patient.
  • Syndrome A group of symptoms as reported by the patient and signs as detected in an examination that together are characteristic of a specific condition.
  • Synergism, Synergistic An interaction between two or more treatments that produces or enhances an effect that is greater than the sum of the effects produced by the individual treatments.
  • Syphilis A primarily sexually transmitted disease resulting from infection with the spirochete (a bacterium) Treponema pallidum. Syphilis can also be acquired in the uterus during pregnancy.
  • Systemic Concerning or affecting the body as a whole. A systemic therapy is one that the entire body is exposed to, rather than just the target tissues affected by a disease.

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T[edit | edit source]

  • T cells (T lymphocytes) T cells are white blood cells derived from the thymus gland that participate in a variety of cell-mediated immune reactions. Three fundamentally different types of T cells are recognized helper, killer, and suppressor. They are essential for a normal functioning immune system.
  • T4 cell (Also called T-helper cell.) Antibody-triggered immune cells that seek and attack invading microorganisms. Macrophages summon T4 cells to the infection site. There, the T4 cell reproduces and secretes potent chemicals that stimulate B cells to produce antibodies, signal natural killer or cytotoxic (cell-killing) T cells, and summon other macrophages to the infection site. In healthy immune systems, T4 cells are twice as common as T8 cells.
  • Teratogenicity The production of physical defects in offspring in utero (i.e., causing birth defects). Teratogenicity is a potential side effect of some drugs, such as thalidomide.
  • Therapeutic HIV vaccine Also called treatment vaccine. A vaccine designed to boost the immune response to HIV infection. A therapeutic vaccine is different from a preventive vaccine, which is designed to prevent an infection or disease from becoming established in a person.
  • Therapy Any form of treatment. Drugs, radiation, and psychiatric counseling are forms of therapy.
  • Thrush Patches in the mouth (sometimes painful) caused by the fungus Candida albicans. Thrush is one of the most frequent early symptoms or signs of an immune disorder. The fungus commonly lives in the mouth, but only causes problems when the body's resistance is reduced either by antibiotics that have reduced the number of competitive organisms in the mouth or by an immune deficiency such as HIV disease. See Candidiasis.
  • Thymus A mass of glandular tissue (lymphoid organ) found in the upper chest under the breastbone in humans. The thymus is essential to the development of the body's system of immunity beginning in fetal life. The thymus processes white blood cells (lymphocytes), which kill foreign cells and stimulate other immune cells to produce antibodies.
  • TID Three times each day.
  • Tissue A collection of similar cells acting together to perform a particular function. There are four basic tissues in the body: epithelial, connective, muscle, and nerve.
  • Titer (Titre) A laboratory measurement of the amount--or concentration--of a given compound in solution.
  • TIW Three times each week
  • TOT Training of trainers.
  • Toxicity The extent, quality, or degree of being poisonous or harmful to the body.
  • Toxoplasmosis (toxo) An opportunistic infection caused by the protozoan parasite Toxoplasma gondii, which is found in undercooked meat and cat feces. A common manifestation is toxoplasmic encephalitis, characterized by brain swelling, confusion, lethargy, and possible coma.
  • Transaminase A liver enzyme (e.g. AST, ALT). A laboratory test that measures transaminase levels to assess the functioning of the liver.
  • Transfusion The process of transfusing fluid (such as blood) into a vein.
  • Transmission In the context of HIV disease, HIV is spread most commonly by sexual contact with an infected partner. The virus can enter the body through the mucosal lining of the vagina, vulva, penis, rectum, or, rarely, the mouth during sex. The likelihood of transmission is increased by factors that may damage these linings, especially other sexually transmitted diseases that cause ulcers or inflammation. HIV also is spread through contact with infected blood, most often by the sharing of drug needles or syringes contaminated with minute quantities of blood containing the virus. Children can contract HIV from their infected mothers either during pregnancy or birth, or postnatally through breast-feeding. HIV is now rarely transmitted by transfusion of blood or blood products because of screening measures.
  • Transplacental Across or through the placenta. Usually refers to the exchange of nutrients, waste products, and other materials (e.g. drugs) between the developing fetus and the mother. Also refers to transmission of virus such as HIV across the placenta to the infant.
  • T-suppressor cells T lymphocytes responsible for turning off the immune response after an infection is cleared. They are a subset of the CD8+ lymphocytes.
  • Tuberculin skin test (TST) A purified protein derivative (PPD) of the tubercle bacilli, called tuberculin, is introduced into the skin by scratch, puncture, or intradermal injection. If a raised, red, or hard zone forms around the test site, the person is said to be sensitive to tuberculin, and the test is read as positive.
  • Tuberculosis (TB) Infection with the bacteria Mycobacterium tuberculosis, as evidenced by a positive tuberculin skin test (TST) that screens for infection with this organism. Sometimes, TST is called a purified protein derivative (PPD) or Mantoux test. A positive skin test might or might not indicate active TB disease. Thus, any person with a positive TST should be screened for active TB and, once active TB is excluded, evaluated for treatment to prevent the development of TB disease. TB infection alone is not considered an opportunistic infection.

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U-V[edit | edit source]

  • UNAIDS Joint United Nations Program on AIDS.
  • Undetectable Usually refers to suppression of the HIV viral load to below the level that laboratory tests can measure, (e.g. <50 copies/mL) through the use of antiretroviral therapy. See Virologic suppression.
  • Universal precautions A simple set of effective practices designed to protect health workers and patients from infection with a range of pathogens, including blood-borne viruses. These practices are used when caring for all patients regardless of diagnosis.
  • Uptake Usually, the numbers of individuals who agree to a procedure such as the number of pregnant women who agree to take an HIV test or agree to participate in prenatal care.
  • Vaccination Inoculation of a substance into the body for the purpose of producing active immunity against a disease. Initially associated with smallpox vaccination but now often used interchangeably with immunization. See Vaccine.
  • Vaccine A substance that contains antigenic components from an infectious microorganism. By stimulating an immune response--but not the disease--it protects against subsequent infection by that organism. There can be preventive vaccines (e.g. measles or mumps) as well as therapeutic (treatment) vaccines. See Therapeutic HIV vaccine; Antigen.
  • Vaginal candidiasis Infection of the vagina caused by the yeastlike fungus Candida (especially Candida albicans). Symptoms include, pain, itching, redness, and white patches in the vaginal wall. It can occur in all women, but it is especially common in women with HIV infection. The usual treatment is a cream applied locally to the vagina. Women with HIV infection may experience frequent reoccurrence of symptoms and may require systemic medications in order to treat these symptoms successfully. See Candidiasis.
  • Varicella-zoster virus (VZV) A virus in the herpes family that causes chickenpox during childhood and may reactivate later in life to cause shingles.
  • VCT Voluntary counseling and testing.
  • VDRL (Venereal Disease Research Laboratory) A test for syphilis.
  • Venipuncture The puncture of a vein (usually in the arm) with a hollow-bore needle for the purpose of obtaining a blood specimen.
  • Viral load The amount of HIV in the circulating blood. Sicker patients generally have more virus than those with less advanced disease. A viral load test is used to monitor the HIV viral burden. Suppression of the HIV viral load is the first goal of antiretroviral therapy (ART), and monitoring a person's viral load is key to assessing the success of ART. See Viral load test; Polymerase chain reaction (PCR); Branched DNA assay.
  • Viral load test In relation to HIV, a test that measures the quantity of HIV RNA in the blood. Results are expressed as the number of copies per milliliter of blood plasma. Viral load testing for HIV infection is used as a test for the presence of HIV and for monitoring the effectiveness of therapy. See Viral load.
  • Viricide Any agent that destroys or inactivates a virus.
  • Virion A virus particle existing freely outside a host cell. A mature virus.
  • Virology The study of viruses and viral disease.
  • Virus Organism composed mainly of nucleic acid within a protein coat. When viruses enter a living plant, animal, or bacterial cell, they make use of the host cell's chemical energy, protein, and nucleic acid-synthesizing ability to multiply. Some viruses do not kill cells but transform them into a cancerous state. Some cause illness and then seem to disappear, while remaining dormant and later causing another, sometimes much more severe, form of disease. In humans, viruses cause measles, mumps, yellow fever, poliomyelitis, influenza, and the common cold, among others. Some viral infections can be treated with drugs.
  • Visceral Involving the major organs inside the body.
  • Voluntary HIV testing An individual is usually counseled regarding HIV prevention and how HIV infection occurs. Participants have the opportunity to accept or refuse HIV testing.

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W-Z[edit | edit source]

  • Wasting syndrome An AIDS-defining condition that is characterized by at least 10% weight loss in the presence of diarrhea, chronic weakness, and documented fever for at least 30 days that is not the result of another infection or disease. In developing countries, it is sometimes called "slim disease."
  • Western blot A laboratory test for specific antibodies to confirm repeatedly positive results on the HIV ELISA or EIA tests. In the United States, Western blot is the validation test used most often for confirmation of these other tests. In developing countries, a rapid HIV test is utilized most commonly. A positive rapid HIV test should be confirmed by a second rapid HIV test made by a different manufacturer.
  • Wild-type virus The original type of HIV, unchanged by having developed any resistance to antiretroviral drugs. Also, the most common type of a virus in the host population before genetic manipulation or mutation; virus that is isolated from a host as opposed to one that is grown in a laboratory culture. See Primary isolate.
  • Window period Time from infection with HIV until antibodies are detected.

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