The following glossary was modified from the glossary on the National Cancer Institute's Web site, available from http://www.nci.nih.gov.

acquired immune deficiency syndrome (AIDS): Infectious disease syndrome that is caused by the human immunodeficiency virus (HIV). Characterized by the loss of a normal immune response and increased susceptibility to opportunistic infections and some cancers.

acquired immunity: Specific immunity that develops after exposure to a particular antigen or after antibodies are transferred from one individual to another.

acyclovir: Synthetic drug with antiviral activity against herpes simplex virus. Often used to treat genital herpes.

aerobe: Organism that can grow in the presence of atmospheric oxygen.

airborne transmission: Transmission of an infectious organism in which the organism is truly suspended in the air and travels a meter or more from the source to the host. Chicken pox, flu, measles, and polio are examples of diseases that are caused by airborne agents.

allergen: Substance that can induce an allergic reaction or specific susceptibility.

amantadine: Antiviral compound sometimes used to treat influenza type A infections.

amebiasis: Infection with amoebae. Usually refers to an infection by Entamoeba histolytica. Symptoms are highly variable, ranging from an asymptomatic infection to severe dysentery.

amphotericin B: Antibiotic used to treat systemic fungal infections and also used topically to treat candidiasis.

anaerobe: Organism that can grow in the absence of atmospheric oxygen.

anthrax: Infectious disease of animals caused by ingesting the spores of Bacillus anthracis. Can occur in humans.

antibiotic: Microbial product, or its derivative, that kills or inhibits the growth of susceptible microorganisms.

antibody: Glycoprotein produced in response to an antigen. Antibodies have the ability to combine with the antigen that stimulated their production.

antibody-mediated immunity: Immunity that results from the presence of antibodies in blood and lymph.

antigen: Foreign (nonself) substance to which lymphocytes respond.

antimicrobial agent: Agent that kills or inhibits the growth of microorganisms.

antiseptic: Chemical applied to tissue to prevent infection by killing or inhibiting the growth of pathogens.

antitoxin: Antibody to a microbial toxin. An antitoxin binds specifically with the toxin, neutralizing it.

arenavirus: Type of RNA virus. Lassa fever is caused by an arenavirus.

autogenous infection: Infection that results from a patient's own microflora.

B-cell: Type of lymphocyte derived from bone marrow stem cells that matures into an immunologically competent cell under the influence of the bone marrow. Following interaction with an antigen, a B-cell becomes a plasma cell, which synthesizes antibodies.

bacillus: Rod-shaped bacterium.

bactericide: Agent that kills bacteria.

binary fission: Asexual reproduction in which a cell separates into two cells.