Carrier - one who carries a virus either in form of an infection or while it is in incubation.

Caspid - The protein outer covering of a virus made up of capsomeres; stimulates the body's immune response.

Cell - a small, enclosed unit containing the DNA, proteins, and chemicals needed for all life functions.

Chromosomes - a DNA containing body that holds most or all of the genes of an individual life form.

Chronic infection - recurring viral infections that cause damage of cells over a long period of time by disrupting their functions.

CNS - the central nervous system, which is comprised of nerves, the brain and the spinal cord.

Connective tissue - tissue that surrounds other more highly ordered tissues and organs; blood, cartilage and bone.

Cytoskeleton - protein filaments that extend through the cytoplasm of cells and enable them to move and change shape.

DNA - deoxyribonucleic acid, the basic component of all living matter, which is contained in the chromosomes of a cell's nucleus; transmits hereditary information and contains gene sequences.

Differentiated - a type of cell, which specializes in one specific task or has one specific purpose.

Dormant - being in a state of suspended animation, not actively growing but protected from the environment.

Electron Microscopy - an imaging method, which uses a focused beam of electrons to enlarge the image of an object on a screen or photographic plate.

Endocytosis - the process in which cells take in fluids or other large molecules.

Enzyme - a type of protein, which catalyzes the reactions between substrates (substances).

Filovirus - The thread-like virus family which includes such viruses as Ebola and Marburg; very deadly.

Genes - a sequence of DNA or RNA that is located on a chromosome and that is the functional unit of inheritance controlling the transmission of traits and function of other genetic material.

Glycoprotein - a compound produced by mixing a protein with any member of a carbohydrate group.

Helper T cells - coordinate the actual immune response of the body; they let other T cells and B cells do their jobs.

Hemorrhagic fever - a condition characterized by non-stop internal or external bleeding resulting from a viral infection which has caused blood vessel damage.

Hereditary material - material responsible for the transmission of qualities from ancestor to descendant through genes.

Host - a living organism, which provides subsistence or lodgment to a parasite.

Humoral immune response - the immune responses mediated by antibodies.

Inactivated vaccine - dead microorganisms used as antigens to produce immunity.

Inclusion bodies - strange and unusual structures found inside a host cell during virus replication.

Infection - the state produced by the presence of an infective agent in or on a suitable host.

Immune System - A body function designed to defend the body from disease causing microorganisms.

Immunity - the condition of being immune, the protection against infectious disease.

Latent infection - viral infection in which the virus responsible is able to avoid the hosts immune system and defenses.

Leukocytes - the majority of the specialized cells used in the immune system; white blood cells.

Lipid - a fatty and oily compound used by cells as energy reserves and material for structure.

Lymph nodes - small bean-shaped organ made up large numbers of lymphocytes, macrophages and accessory cells located along the lymphatic system

Lymphoid tissue - tissue made up white blood cells and special fibers.

Lysis - the cell membrane of a host is completely destroyed and newly replicated viruses are unleashed instantaneously.

Macrophage - contains lysosomes full of special enzymes and chemicals, which allows it to ingest and digest dangerous microbes

Memory cells - keep the body prepared for the next struggle with antigens that have already been encountered.

mRNA (messenger RNA) - used as the carrier of genetic codes and information directly from DNA to cell structures.

Mutation - a rearrangement of genes or change in base pairs so they produce different effects within their environment.

Nanometer - One-millionth of a millimeter.

Nucleic acid - an organic compound made up of a phosphoric acid, a carbohydrate and a base of purine or pyrimidine; formed in helical chains.

Nucleus - a cellular organelle that is the essential control mechanism for cell function; contains the DNA and genetic material.

Origin - location where the process of replication in a nucleic acid begins.

Parasite - an organism living in or on another organism that depends on its host for existence or support and gives nothing in return.

Pathogenesis - the growth and development of a disease.

Prion - an infectious crystallizing protein, which affects the brain.

Proteins - strands of amino acids which make the enzymes and structures needed for cells to grow and function properly.

RNA (ribonucleic acid) - strings of organic material, obtained from DNA, which store the proper instructions necessary to produce amino acids.

Receptor - a structure on a cell which joins with proteins to produce changes in cellular function.

Replication - the action or process of reproducing exact copies of one's self.

Retrovirus - An RNA virus that converts its RNA into DNA by means of the enzyme reverse transcriptase and integrates itself directly into the host's DNA.

Reverse transciptase - special enzyme which allows retroviruses to translate genetic code from RNA to DNA.

Ribosome - the spherical structure that assembles proteins after being fed the genetic instructions by mRNA.

Spleen - an organ that produces lymphocytes, filters the blood, and stores blood cells

Strain - a specific type, quality, or disposition of a material.

Suppressor T cells - monitor and adjust antibody levels in the body; act as suppressors to counteract the Helper and Killer T cells at the end of infections.

Thymus - The lymphoid organ in which T lymphocytes are educated, mature and multiply.

T lymphocyte cells - thymus dependent cells, coordinate the cell-mediated immune system.

Transcription - constructing a mRNA molecule using a DNA molecule as a template; results in the transfer of genetic information to the mRNA.

Vaccine - Weakened or destroyed microorganisms used to help provide immunity to a certain disease or microorganism and to stimulate the production of antibodies.

Variant - a variation of a particular strain of virus or infective agent; slightly different in form or function.

Vector - anything capable of moving or transferring genetic material.

Viroid - exotic type of virus which only infects plant cells and is simply a group of naked strings of amino acids with no covering.

Virus - infectious organism that replicates itself in the cells of a host; viruses have a half alive/half dead existence and need a host to grow and reproduce.