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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safer sex: sexual activities that reduce or eliminate the exchange of body fluids that can transmit HIV by means of barriers such as latex condoms, gloves, and dental dams.
salvage therapy: emergency therapy, usually with experimental drugs or a multidrug regimen, of an illness that has not responded (or has ceased to respond) to previous attempts at treatment.
sample size: the number of participants in a clinical trial.
saquinavir (brand name Invirase, brand name Fortovase): a protease inhibitor drug approved for use as part of combination antiretroviral therapy to treat HIV disease.
sarcoma: a malignant tumor of the skin or soft tissue.
SCID mouse: a mouse lacking key immune system components that is used as an animal model in the study of immune disorders.
SDF-1 (aka stromal cell-derived factor): a chemokine that binds to the cell surface receptor CXCR4, a coreceptor for certain strains of HIV.
secondary infection: infection with a second or subsequent infectious organism during the course of an initial infection.
secondary prophylaxis: therapy to prevent a subsequent occurrence (relapse) of a disease or condition. Compare with primary prophylaxis.
second-line treatment: the second preferred therapy for a particular condition, used after first-line treatment fails or if a person cannot tolerate first-line drugs.
sed rate: See erythrocyte sedimentation rate.
selective serotonin reuptake inhibitor (acronym SSRI): a class of commonly used antidepressants (e.g., fluoxetine [Prozac], citalopram [Celexa], sertraline [Zoloft]) that increase levels of the neurotransmitter serotonin.
semen: a whitish, viscid fluid ejaculated from the penis containing spermatozoa and secretions from the prostate gland.
sensitivity: the ability of an organism to respond to a drug or other agent; a statistical measure of the accuracy of a screening test, that is, how likely a test is to label as positive those who have a disease or condition.
Contrast with specificity.
sensory neuropathy: damage or necrosis of the sensory nerves, resulting in numbness, tingling, or pain in the extremities. See also peripheral neuropathy.
sepsis: the presence of pathogenic organisms (e.g., bacteria, fungi) or their toxins in the blood or tissues. See also septicemia.
septicemia: blood poisoning; a condition associated with the presence of pathogenic organisms or their toxins in the blood or tissues. Septic shock refers to decreased blood pressure and organ failure due to sepsis.
Septra: Brand name of trimethoprim-sulfamethoxazole.
sequelae: conditions resulting from a disease or injury.
seroconversion: change in an individual's serostatus from negative to positive; development of antibodies against a microorganism. Contrast with seroreversion.
serology (adjective serological): the study or analysis of blood, in particular the clear fluid portion of blood; tests that measure components (e.g., microorganisms, antibodies, chemicals) in the blood.
seronegative: See serostatus.
seropositive: See serostatus.
seroprevalence: the rate of infected individuals in a given population as determined by blood antibody tests; the number of infected individuals divided by the total population.
seroreversion: change in an individual’s serostatus from positive to negative; absence of antibodies against a microorganism after they were previously detectable.
Contrast with seroconversion.
serostatus: the presence or absence of antibodies against a pathogenic microorganism in the blood. If antibodies are present (indicating exposure to or infection with a pathogen), an individual is seropositive; if not, the individual is seronegative.
serotonin: a neurotransmitter (neural messenger) that has many effects, including blood vessel constriction and mood regulation.
serum: the fluid portion of blood that remains after cells are removed; lymphatic fluid.
set point: the initial baseline viral load level, measured after the acute burst of viral replication following seroconversion has subsided.
sexually transmitted disease (acronym STD, aka sexually transmitted infection, aka venereal disease): any disease (e.g., gonorrhea, syphilis, chlamydia, genital herpes) transmitted through sexual contact.
SGOT: See aspartate aminotransferase.
SGPT: See alanine aminotransferase.
shedding: release of infectious particles (e.g., bacteria, viruses) into the environment, for example, by sneezing, fecal excretion, or from an open lesion.
shingles: See herpes zoster.
shock: a condition characterized by decreased blood pressure and inadequate oxygen delivery to the tissues; circulatory collapse; symptoms of shock include pallor (paleness); thirst; cool, clammy skin; and weak, rapid pulse.
short-course therapy: a therapeutic regimen given for a shorter than usual period of time.
SI: See syncytium-inducing (SI) strain.
side effect: any unintended or extraneous effect of a drug or therapy; generally refers to a negative or undesired event. See also adverse event.
sigmoidoscopy: examination of the sigmoid colon (the lower transverse part of the colon) with a lighted, flexible viewing instrument. See also proctoscopy.
sign: an externally visible or measurable manifestation of a disease or condition.
Compare with symptom.
SIL: See squamous intraepithelial lesion.
simian: refers to monkeys.
simian immunodeficiency virus (acronym SIV): a virus similar to HIV that infects monkeys.
single-blind: See blinding.
SIV: See simian immunodeficiency virus.
slim disease: a term for AIDS used in parts of Africa, so called because of the wasting effects of the disease.
sodium: a trace element that is essential for many bodily processes, including proper neural transmission.
soluble: capable of being dissolved.
solvent: an agent that dissolves.
somatic: refers to the physical body.
somatotropin:
See human growth hormone.
specific immunity (aka adaptive immunity): antigen-specific immune defense carried out by lymphocytes (e.g., B cells and T cells), which respond to specific pathogens; the two types of specific immunity are cell-mediated (Th1 response) and humoral (antibody-mediated, or Th2 response). Compare with nonspecific immunity.
specificity: a statistical measure of the accuracy of a screening test, that is, how likely a test is to identify as negative those who do not have a disease or condition.
Contrast with sensitivity.
spike: a sudden increase in viral load; a protein protrusion on the outer envelope of a virus.
spinal cord: the length of nervous tissue that extends from the base of the brain to the lower back through the spinal vertebrae, carrying impulses to and from the brain.
spinal tap:
See lumbar puncture.
spleen (adjective splenic): an immune system organ located in the abdominal cavity that produces blood cells in the fetus and later removes old red blood cells and platelets from circulation and acts as a site of lymphocyte activation.
splenectomy: surgical removal of the spleen.
sputum: mucous coughed up from the bronchial tubes and lungs; a sputum smear is a diagnostic test that detects microorganisms (e.g., Mycobacterium tuberculosis) in the sputum.
squamo-columnar junction: See transformation zone.
squamous cells: flat, thin cells that comprise the surface of the skin and mucous membranes.
squamous intraepithelial lesion (acronym SIL): abnormal growth of epithelial cells (e.g., in the uterine cervix or anal canal). Low-grade SIL (LSIL or LGSIL) refers to mild cellular changes; high-grade SIL (HSIL or HGSIL) refers to more severe, precancerous changes. See also intraepithelial neoplasia.
SSRI: See selective serotonin reuptake inhibitor.
standard deviation: a statistical measure of variability.
standard of care: the level of care which all persons with a particular illness should receive; the level below which care would be considered inadequate.
standard therapy: a therapy that is FDA-approved for a specific condition and is widely used as first-line treatment for that condition.
statin: a class of drugs (e.g., atorvastatin [Lipitor], pravastatin [Pravachol]) used to reduce levels of blood lipids, especially cholesterol.
statistical significance: the probability that the outcome of an experiment or clinical trial is not solely due to chance; typically, a clinical trial result is considered statistically significant if there is a less than a 5% probability (designated by a p-value of less than .05) that the observed outcome could have occurred by chance alone if the treatments being compared were equally effective.
stavudine: generic name of d4T.
STD: See sexually transmitted disease.
steatosis: accumulation of fat in an organ, especially the liver.
stem cell: an undifferentiated precursor cell that gives rise to other types of cells; pluripotent stem cells are immature blood cells, located in the bone marrow, that evolve into mature red and white blood cells and platelets.
steroid: one of a family of hormones and related natural or synthetic compounds that share a similar chemical structure. Some steroid hormones (e.g., estrogen, testosterone) influence the development and function of the sex organs (ovaries and testes); anabolic steroids promote the development of muscle mass. See also corticosteroid.
Stevens-Johnson syndrome: a severe form of erythema multiforme; an uncommon, potentially life-threatening hypersensitivity reaction (typically caused by a drug or by certain infections) characterized by fever and flu-like symptoms followed by a severe, blistering rash on the skin and mucous membranes, and sometimes also tissue necrosis, eye lesions, and/or internal organ damage. See also toxic epidermal necrolysis.
strain: a specific genetic variant of a particular organism. See also subtype.
stroke (aka cerebrovascular accident): an interruption of the supply of blood to parts of the brain, potentially leading to a loss of physical or mental function (e.g., vision, speech, or motor impairment, partial paralysis).
structured treatment interruption (acronym STI): stopping and restarting therapy on a specified, monitored schedule.
sub-: prefix meaning below.
subclinical: low-grade and asymptomatic.
subcutaneous: beneath the skin; subdermal.
subgroup analysis: additional analysis of a smaller group of participants (e.g., based on demographic characteristics, clinical status) selected from a larger study population.
subject: a volunteer participant in a clinical trial.
sublingual: under the tongue.
subtherapeutic: refers to a dose or blood concentration of a drug that is too low to be effective.
subtype (aka clade): a phylogenetically distinct strain of a microorganism. HIV-1 is classified into three groups (M, N, and O), which in turn are made up of various subtypes. See also strain.
superinfection: acquisition of a second or subsequent infection with a particular organism while an initial infection is still present; superinfection with HIV appears to worsen disease progression. Compare with coinfection.
suppression: See viral suppression.
suppressor T cell: a type of T cell that bears the CD8 cell surface marker and helps regulate immune function by inhibiting antibody production and the activity of cytotoxic T lymphocytes.
surrogate marker: a marker or sign that can serve in place of a clinical endpoint such as disease progression or death; surrogate markers for HIV disease may be virological (e.g., viral load), immunological (e.g., CD4 cell count), or clinical (e.g., weight loss).
survival rate: the percentage of a population or study group that remains alive after a given period.
susceptible: vulnerable to or able to contract a disease; vulnerable to the effects of a drug. Contrast with resistance.
sustained virological response (acronym SVR):
See virological response.
Sustiva: brand name of efavirenz.
SVR: See virological response.
symptom (adjective symptomatic): a subjectively perceptible sensation or change that signals the presence of a disease or condition.
Compare with sign.
syncytia (singular syncytium): clumps of cells whose membranes have fused together to form "giant cells." HIV strains are classified as either syncytia-inducing (SI), which tend to infect T lymphocytes and are associated with more rapid disease progression, or non-syncytia-inducing (NSI), which tend to infect macrophages and are associated with milder disease.
syncytium: an abnormal "clump" of fused cells.
syncytium-inducing (SI) strain: an aggressive strain of HIV that preferentially infects T-cells (therefore called "T-tropic" virus); generally less susceptible to antiretroviral drugs and associated with more rapid disease progression. See also syncytium. Contrast with non-syncytium-inducing (NSI) strain.
syndrome: a set of symptoms or disease manifestations that occur together and characterize a specific condition.
syndrome X: See metabolic syndrome.
synergy (adjective synergistic): an interaction between agents (e.g., drugs) that produces an effect greater than the combined effects of the same agents used separately.
synthesis: production.
synthetic: produced artificially; man-made.
syphilis: sexually transmitted infectious disease caused by the Treponema pallidum bacterium; the disease progresses through several stages, including primary syphilis (characterized by a painless chancre, typically in the anogenital area), secondary syphilis (characterized by a skin rash that includes the palms and soles), a dormant stage, and tertiary syphilis (which may affect many organs, including the brain, leading to dementia [neurosyphilis] and death).
systemic: affecting the whole body.
systemic lupus erythematosus (acronym SLE): an autoimmune disease characterized by inflammation of the connective tissue, especially in the joints.
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