(Italicized terms are also deﬁned within this glossary or the glossary of Key Immunology Terms.)
acquired immunodeﬁciency syndrome (AIDS): a disease of the immune system that is caused by infection with human immunodeﬁciency virus (HIV), commonly transmitted in blood and body secretions such as semen. People with AIDS are highly vulnerable to life-threatening infections.
Alzheimer’s disease: a degenerative brain disease of unknown cause and the most common form of dementia. Alzheimer’s disease usually starts in late middle age or in old age as memory loss involving recent events, then progresses over the course of ﬁve to ten years to a profound intellectual decline characterized by dementia and personal helplessness.
amyotrophic lateral sclerosis (ALS): a rare, fatal, progressive degenerative disease that affects pyramidal motor neurons (responsible for all voluntary movements), characterized especially by increasing and spreading muscular weakness. ALS, also called Lou Gehrig’s disease, usually appears in middle age.
asthma: a condition often of allergic origin that is marked by labored breathing accompanied by wheezing and a sense of constriction in the chest, and often by attacks of coughing or gasping.
athlete’s foot: a foot rash caused by a fungus.
autism: a mental disorder that appears at a young age and is characterized by self-absorption, inability to interact socially, repetitive behavior, and language difﬁculty.
bird ﬂu: (also avian inﬂuenza); any of several highly variable diseases of domestic and wild birds, caused by viruses and usually characterized by respiratory symptoms.
cancer: a malignant tumor of potentially unlimited growth that expands locally by invasion and can spread throughout the body in a process called metastasis.
chicken pox: a contagious disease, usually in children, caused by a virus and marked by low-grade fever and the formation of blisterlike spots; also called varicella.
chronic lung disease: one of a group of recurrent diseases of the lower respiratory tract.
coronary artery disease: a condition that reduces the blood ﬂow through the coronary arteries to the heart muscle; also called coronary disease, coronary heart disease.
cowpox: a mild disease in cows that is caused by a poxvirus and that protects against a related virus, smallpox, when injected as a vaccine into humans.
Crohn’s disease: a disease of the small intestine that often spreads to the colon, part of the large intestine. Crohn’s disease is characterized by diarrhea, cramping, and loss of appetite and weight, with local abscesses and scarring.
diabetes: abnormal condition characterized by a lack of insulin or a resistance to insulin. The excretion of excessive amounts of urine is an early symptom.
gonorrhea: a contagious inﬂammation of the genital mucous membrane caused by the gonococcus bacterium.
hantavirus: any of a group of closely related viruses that cause a respiratory disease or fever accompanied by leakage of plasma and red blood cells through the lining of blood vessels and by the death of kidney tissue.
hepatitis A: a usually benign inﬂammation of the liver, caused by an RNA-containing virus that does not persist in the blood serum. Hepatitis A is transmitted especially in food and water contaminated with fecal matter.
hepatitis C: a disease that inﬂames the liver, caused by a single-stranded RNA-containing virus and usually transmitted by exposure to blood or blood products. Hepatitis C leads eventually to scarring in the liver and liver cancer.
herpes: inﬂammatory diseases of the skin caused by one of several herpes viruses and characterized by clusters of blisters.
human immunodeﬁciency virus (HIV): a retrovirus that infects and destroys CD4+ helper T cells in the immune system, causing the marked reduction in their number and thus lowering resistance to life-threatening infections that characterize AIDS.
Lyme disease: an acute inﬂammatory disease that is usually characterized initially by skin lesions, fatigue, fever, and chills, and if left untreated may later manifest itself in cardiac and neurological disorders, joint pain, and arthritis. Lyme disease is caused by a bacterium transmitted by the bite of a tick.
malaria: a disease caused by the presence of the organism Plasmodium in human or other vertebrate red blood cells, usually transmitted to humans by the bite of an infected female mosquito that previously sucked blood from a person with malaria. The disease is characterized by episodic severe chills, high fever, and exhaustion; it can be fatal.
measles: a contagious viral disease that begins with conjunctivitis (pinkeye), coughing, and spots in the mouth. Measles is marked by the appearance on the third or fourth day of an eruption of distinct red circular bumps that gradually diminish after another four days, and much less frequently by serious inﬂammation of the brain (encephalitis).
mononucleosis: an infectious disease associated with the Epstein-Barr virus; characterized by fever, swelling of lymph nodes, and an abnormal increase of single-nucleus white blood cells (accounting for the preﬁx “mono-”).
multiple sclerosis: a disease marked by patches of hardened tissue in the brain and on the spinal cord that causes the destruction of the nerves’ protective myelin sheath. Partial or incomplete paralysis and jerking muscle tremor can result.
mumps: a contagious disease caused by a paramyxovirus and marked by fever and swelling, especially of the parotid glands.
Parkinson’s disease: a chronic, progressive nervous system disease that usually appears later in life and is linked to decreased dopamine production in the substantia nigra brain region. Parkinson’s disease is marked by tremor and weakness of resting muscles and by a shufﬂing gait.
primary immune deﬁciency (PID) diseases: diseases caused by an inherited genetic defect that interferes with the immune system’s normal development.
rabies: highly fatal infectious disease transmitted by the bite of infected animals, including dogs, cats, foxes, raccoons, and bats, and caused by a virus in the central nervous system and the salivary glands. The symptoms are characteristic of a profound disturbance of the nervous system: excitement, aggressiveness, and madness, followed by paralysis and death.
rheumatoid arthritis: a usually chronic autoimmune disorder characterized especially by pain, stiffness, inﬂammation, swelling, and sometimes destruction of joints.
rubella (German measles): a contagious viral disease that is milder than typical measles but is damaging to the fetus when it occurs early in pregnancy.
scleroderma: a disease, usually slow to progress, characterized by ﬁbrous connective tissue in the skin and, frequently, internal organs. Symptoms include sensitivity to cold and tightening and thickening skin.
selective immunoglobulin A deﬁciency (selective IgA deﬁciency): a condition that results when B lymphocytes, a type of white blood cell,do not mature properly and fail to produce immunoglobulin A antibodies at the levels required. People with the condition can be healthy or suffer recurrent lung, ear, and sinus infections.
severe acute respiratory syndrome (SARS): a severe form of pneumonia, caused by a virus, that appeared in outbreaks in 2003.
severe combined immunodeﬁciency disease (SCID): a rare, congenital disorder of the immune system characterized by the inability of B cells and T cells to produce a normal complement of antibodies; usually results in early death.
smallpox: a contagious disease characterized by fever, pus-ﬁlled bumps on the skin, separation of dead tissue, and scar formation; caused by a poxvirus that is believed to exist now only in lab cultures.
systemic lupus erythematosus: an inﬂammatory autoimmune disease of unknown cause that leads to the production of autoantibodies, or antibodies that recognize and attack the body’s own components. Occurring chieﬂy in women, it is characterized especially by fever, skin rash, and arthritis; often by anemia, in which red blood cells are destroyed; by small hemorrhages in the skin and mucous membranes; by inﬂammation of the pericardium (the sac around the heart); and in serious cases by involvement of the kidneys and central nervous system.
toxic shock syndrome: a sometimes fatal disease characterized by fever, nausea, diarrhea, skin redness, and shock. The syndrome is associated especially with the presence of the bacterium Staphylococcus aureus, which produces a toxic protein, and occurs especially in menstruating females using tampons.
tuberculosis: a highly variable disease caused by the tubercle bacterium or, rarely in the United States, a related bacterium. Usually transmitted by inhalation of airborne bacteria, it affects the lungs but may spread to other areas, especially the brain, from local lesions or by way of the lymph or blood vessels. Tuberculosis is characterized by fever, coughing, difﬁculty in breathing, and inﬂammation.
turista: also called traveler’s diarrhea; intestinal sickness typically caused by ingesting microorganisms such as E. Coli.
West Nile: disease caused by a virus spread chieﬂy by mosquitoes that causes an illness marked by fever, headache, muscle ache, skin rash, and sometimes encephalitis or meningitis.
whooping cough: also called pertussis; an infectious disease especially of children that is caused by a bacterium and is marked by a convulsive, spasmodic cough, sometimes followed by a shrill intake of breath. Whooping cough is one of the targets of the diphtheria-pertussis-tetanus (DPT) vaccine.