Glossary of HIV/AIDS Terms
This glossary contains 1,600 terms and is maintained by the editors of the San Francisco AIDS Foundation's Bulletin of Experimental Treatments for AIDS.
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HAART: highly active antiretroviral therapy, a term for potent combination anti-HIV treatment, usually with three or more drugs from different classes.
habitus: body build and constitution; physical or constitutional characteristics.
half-life: the time required for half the total amount of a substance (e.g., drug) or microorganism to be eliminated from the body.
HAV: See hepatitis A.
HBIG: hepatitis B immune globulins, antibodies used as postexposure prevention against hepatitis B.
HBV: See hepatitis B.
HCT: See hematocrit.
HCV: See hepatitis C.
HDL: See cholesterol.
heart attack: See myocardial infarction.
helicase: an enzyme that unwinds the DNA helix into single strands, thereby facilitating replication.
helicase inhibitor: an agent that blocks the action of the helicase enzyme.
helminth: a wormlike parasite.
helper T cell: See CD4 cell.
hematocrit (acronym HCT): the percentage of red blood cells in a given amount of whole blood; a measure the oxygen-carrying capacity of the blood; red blood cells normally constitute about 40-55% of whole blood in men and about 35-45% in women.
hematology (adjective hematological): the study of blood and blood-forming tissues.
hematopoiesis: the production of new blood cells in the bone marrow; hematopoietic stem cells give rise to all types of blood cells.
hematotoxic: poisonous to the blood or the blood-producing stem cells in the bone marrow.
hemoglobin (acronym HGB): the red, iron-based pigment in red blood cells that enables them to transport oxygen; normal hemoglobin values are 14-18 grams/dL in men and 12-16 grams/dL in women.
hemolysis: the breakdown or destruction of red blood cells.
hemophilia: a hereditary disease in which an individual lacks factors necessary for normal blood clotting, leading to easy bleeding and bruising.
hemorrhage: loss of a large amount of blood.
HEPA filter: high-efficiency particulate air filter, a type of filter that helps prevent airborne transmission of diseases such as tuberculosis.
hepatic: refers to the liver.
hepatic encephalopathy: impaired brain function due to advanced liver damage, occurring when the liver can no longer effectively filter toxins from the bloodstream.
hepatic panel: See liver function tests.
hepatitis: inflammation of the liver; hepatitis may be caused by several factors, including viruses (hepatitis A, B, C, D, and E), toxic substances, heavy alcohol use, and certain drugs; hepatitis symptoms may include fatigue, loss of appetite, abdominal tenderness, jaundice, and elevated liver enzymes (ALT and AST).
hepatitis A (acronym HAV, aka infectious hepatitis): a viral disease of the liver with a short incubation period that is primarily transmitted through the fecal-oral route. Hepatitis A typically resolves on its own and does not become chronic; there is no standard treatment, but an HAV vaccine is available.
hepatitis B (acronym HBV, aka serum hepatitis): a blood-borne viral disease of the liver. Hepatitis B becomes chronic in about 5-10% of infected adults and 90% of infected infants; untreated chronic HBV can lead to cirrhosis and liver cancer. Standard treatments are interferon, 3TC, and adefovir; an HBV vaccine is available.
hepatitis B immunoglobulin (acronym HBIG): a preparation of antibodies administered as postexposure prophylaxis to prevent illness in people exposed to the hepatitis B virus.
hepatitis C (acronym HCV, formerly non-A, non-B hepatitis): a blood-borne viral disease of the liver. Hepatitis C becomes chronic in as many as 85% of infected individuals; untreated chronic HCV can lead to cirrhosis and liver cancer. Standard treatment is pegylated interferon plus ribavirin; there is no HCV vaccine.
hepatitis D (acronym HDV, aka delta hepatitis): a blood-borne viral disease of the liver; hepatitis D only occurs in individuals who are also infected with hepatitis B.
hepatitis E (acronym HEV): a viral disease of the liver that is primarily transmitted through the fecal-oral route; hepatitis E is rare in the U.S., but common in parts of Africa and Asia. The disease is usually mild and self-limiting, but may be severe in pregnant women.
hepatitis G (acronym HGV): See GBV-C.
hepatocellular carcinoma (acronym HCC): a type of liver cancer that may result from chronic hepatitis.
hepatocyte: a liver cell.
hepatology: the medical specialty concerned with the liver and its disorders.
hepatomegaly: liver enlargement.
hepatotoxic (noun hepatotoxicity): poisonous or harmful to the liver.
Hepsera: brand name of adefovir.
herbal therapy: the therapeutic use of plants or plant products to treat or prevent illness.
herpes simplex virus (acronym HSV): a herpesvirus that causes recurring lesions. Herpes simplex virus type 1 (HSV-1) typically produces blisters on the lips or in the mouth (cold sores or fever blisters), while HSV type 2 (HSV-2) is typically sexually transmitted and produces lesions in the genital or anal area; however, either virus can infect either region. In healthy individuals, lesions usually resolve without treatment within 2-3 weeks; in immunocompromised persons, lesions may last longer and outbreaks may be more frequent.
herpes zoster (aka shingles): a condition characterized by painful blisters caused by reactivation of varicella-zoster virus (VZV). Blisters typically appear in a dermatomal (linear) distribution on the skin following nerve pathways; outbreaks occur more frequently and may be more severe in immunocompromised individuals.
herpesvirus (aka herpetoviridae): a group of viruses that includes herpes simplex virus type 1 (HSV-1, or HHV-1) and type 2 (HSV-2, or HHV-2); varicella-zoster virus (VZV, or HHV-3); Epstein-Barr virus (EBV, or HHV-4); cytomegalovirus (CMV, or HHV-5); human herpesvirus types 6 and 7 (HHV-6, HHV-7); and Kaposi's sarcoma-associated herpesvirus (KSHV, or HHV-8). Herpesviruses may act as opportunistic pathogens in people with compromised immune systems.
heterozygous: possessing two different alleles, or gene variants, at a given site on a chromosome. Contrast with homozygous.
HGH: See human growth hormone.
high-density lipoprotein (acronym HDL): See cholesterol.
hirsutism: excessive growth of bodily and facial hair.
histamine: a cytokine released by basophils and mast cells in response to exposure to a foreign antigen; histamine causes blood vessel dilation, decreases blood pressure, mediates allergic reactions, and regulates stomach acid production.
histocompatibility: immunological similarity; histocompatibility testing compares the HLA “self” markers of a tissue donor and a recipient to determine whether they are a good match, that is, whether the recipient is likely to accept, rather than reject, a transplant. See also human leukocyte antigen. See also major histocompatibility complex.
histology (adjective histological): the study or examination of body tissues; histological improvement refers to improved tissue health.
histoplasmosis: a fungal infection caused by the fungus Histoplasma capsulatum, which is present in soil or dust; the disease most often affects the lungs, where it produces a tuberculosis-like inflammation, but may also disseminate.
historical control: use of medical records to compare a current treatment with a treatment used in the past.
HIV: See human immunodeficiency virus.
HIV disease: disease or illness caused by infection with the human immunodeficiency virus; if untreated, the disease typically progress slowly from asymptomatic infection to worsening immunocompromise to full-blown AIDS.
HIV encephalopathy: See AIDS dementia complex.
HIV negative: See serostatus.
HIV positive: See serostatus.
HIV-associated dementia: See AIDS dementia complex.
Hivid: brand name of ddC.
HLA: See human leukocyte antigen.
Hodgkin’s disease: a type of lymphoma (cancer of the lymphatic system) characterized by the presence of Reed-Sternberg cells, enlarged lymph nodes and spleen, wasting, fever, and anemia.
holism (adjective holistic): an alternative treatment system that focuses on the whole person rather than on specific diseases or disorders, and considers physical, emotional, social, environmental, and spiritual factors.
homeopathy: a treatment methodology based on the theory that "like cures like." Homeopathic therapy uses extremely small, diluted doses of substances that normally cause the types of symptoms being treated.
homeostasis: maintenance of equilibrium or a stable bodily state.
homozygous: possessing two copies of the same allele, or gene variant, at a given site on a chromosome. Contrast with heterozygous.
horizontal transmission: spread of an infectious disease from one individual to another within a population. Compare with mother-to-child transmission.
hormone: a chemical messenger (e.g., adrenaline, testosterone) involved in the regulation and coordination of cellular and bodily functions; hormones may act locally (exocrine) or be secreted into the bloodstream (endocrine). The term may also refer to any type of chemical messenger, including, for example, cytokines and neurotransmitters.
hormone replacement therapy (acronym HRT): the administration of exogenous hormones to replace those the body is unable to produce; HRT most often refers to the replacement of estrogen and progesterone following menopause.
host cell: a cell infected with a virus or other microorganism.
HPV: See human papillomavirus.
HRT: See hormone replacement therapy.
HSV: See herpes simplex virus.
HTLV-III: one of the early names given to the virus now known as HIV.
human growth hormone (acronym HGH, aka somatotropin, brand name Serostim): a peptide hormone secreted by the anterior pituitary gland that promotes growth by stimulating metabolism and protein synthesis; recombinant HGH is used to treat wasting and enhance muscle development.
human herpesvirus 1, 2: See herpes simplex virus.
human herpesvirus 3: See varicella-zoster virus.
human herpesvirus 4: See Epstein-Barr virus.
human herpesvirus 5: See cytomegalovirus.
human herpesvirus 6, 7 (acronym HHV-6, acronym HHV-7): two herpesviruses that can cause fever and skin rash in young children, and have been hypothetically linked to several conditions, including chronic fatigue syndrome.
human herpesvirus 8 (acronym HHV-8): See Kaposi’s sarcoma-associated herpesvirus.
human immunodeficiency virus (acronym HIV): a slow-acting blood-borne retrovirus of the lentivirus family, believed to be the sole or primary cause of AIDS. There are two major types, HIV-1 and HIV-2, and many subtypes of the virus. HIV-1 is prevalent throughout most of the world; HIV-2 is found mostly in West Africa and typically causes a milder form of immunodeficiency disease.
human leukocyte antigen (acronym HLA): a genetic marker of "self" that prevents the immune system from attacking the body’s own tissues. See also major histocompatibility complex.
human papillomavirus (acronym HPV): a papovavirus associated with abnormal cell growth. Several HPV strains cause warts, including condylomata acuminata (genital warts); certain other strains (e.g., 16, 18) are associated with cervical, anal, and oral cancer.
humoral immunity (aka antibody-mediated immunity): a type of immune response based on antibodies, which are produced by B cells. See also Th2 immune response. Compare with cell-mediated immunity.
hydroxyurea (brand name Hydrea): a drug that interferes with viral replication by inhibiting the activity of ribonucleotide reductase, thereby reducing the supply of the nucleotide building blocks needed to synthesize new DNA.
hyper-: prefix meaning above, excessive, or elevated.
hyperbilirubinemia: an elevated level of bilirubin in the blood, characterized by jaundice; hyperbilirubinemia may be a sign of liver or gall bladder dysfunction.
hypercholesterolemia: an elevated level of cholesterol in the blood.
hyperglobulinemia: an abnormally high level of antibodies in the blood.
hyperglycemia: high blood glucose (sugar).
hyperlactatemia: elevated blood level of lactic acid (lactate) due to increased production or decreased clearance of the chemical; mild hyperlactatemia is usually asymptomatic, but may progress to frank lactic acidosis.
hyperlipidemia: elevated levels of blood fats (e.g., triglycerides, cholesterol).
hyperplasia: excessive growth of normal cells (i.e., not tumor or cancer cells).
hyperproliferation: rapid or excessive growth and reproduction.
hypersensitivity: abnormal sensitivity or susceptibility; a hypersensitivity reaction is an exaggerated immune response, for example a severe drug reaction.
hypertension: high blood pressure.
hyperthyroidism: excessive thyroid hormone production, characterized by increased metabolic rate, enlargement of the thyroid gland, rapid heart rate, and high blood pressure.
hypertriglyceridemia: an elevated level of triglycerides (fatty acid compounds) in the blood.
hypertrophy: excessive growth or enlargement.
hypo-: prefix meaning beneath, subnormal, or low.
hypoadrenalism (aka adrenal insufficiency): inadequate adrenal function, resulting in low levels of adrenal hormones.
hypogammaglobulinemia: low level of antibodies in the blood.
hypoglycemia: low blood glucose (sugar).
hypogonadism: reduced activity of the gonads (ovaries or testes); low levels of gonadal hormones such as testosterone.
hypometabolism: abnormally low metabolic level.
hypothalamus: a gland in the brain that regulates the autonomic nervous system; the hypothalamus controls metabolic rate and body temperature, helps regulate hunger, and promotes the production of endocrine hormones.
hypothyroidism: decreased activity and hormone secretion by the thyroid gland, characterized by weight gain, sluggishness, and decreased metabolism.
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