Test Prep - Infectious disease

Pathogen

An invading biological agent or organism that causes infectious disease in a host.

Infectious Disease

A disease caused by a pathogen that can be transmitted from one organism to another.

Non-Infectious Disease

A disease not caused by a pathogen, arising instead from genetics, environment, or lifestyle.

Prion

A non-cellular, infectious, misfolded protein containing no nucleic acids that alters normal brain proteins.

Virus

A non-cellular pathogen consisting of a protein capsid surrounding DNA or RNA; requires a host cell to replicate.

Bacteria

Unicellular, prokaryotic organisms lacking a nucleus, featuring a circular chromosome and peptidoglycan cell wall.

Fungi

Unicellular or multicellular eukaryotic organisms containing chitin cell walls that reproduce via spores.

Protist

Unicellular, eukaryotic organisms that lack cell walls and are often motile.

Parasite

An organism that lives on or inside a host, deriving nutrients at the host's expense.

Direct Transmission

Immediate transfer of a pathogen from an infected host to a susceptible host via physical contact.

Indirect Transmission

Transfer of a pathogen from a reservoir to a host via intermediate vectors, droplets, or fomites.

Vector

An intermediate organism, usually an arthropod, that transmits a pathogen from host to host without getting sick.

Fomite

An inanimate object capable of carrying and transferring infectious pathogens.

Droplet Transmission

Pathogen transfer via respiratory aerosols expelled through coughing, sneezing, or talking.

Epidemic

A sudden increase in cases of an infectious disease above what is normally expected in a specific population.

Pandemic

An epidemic that has spread globally across multiple countries or continents, affecting large numbers of people.

Virulence

The degree of pathogenicity or ability of an infectious agent to cause severe disease.

Host Density

The number of host individuals per unit area, which increases pathogen contact and transmission rates.

Herd Immunity

Resistance to a disease spread within a population when a critically high percentage of individuals are immune.

Quarantine

The isolation of individuals suspected of exposure to a pathogen to prevent potential transmission.

Vector Control

Eradication or management of vector populations to break the transmission cycle of a disease.

Antibiotic

A chemical substance that kills or inhibits the growth of bacteria by targeting specific bacterial structures.

Antiviral

A medication that inhibits specific steps of viral replication within host cells without destroying the host cell.

Antiseptic

A chemical agent applied to living tissue to kill or inhibit the growth of pathogens.

Disinfectant

A chemical agent applied to non-living surfaces to destroy pathogens.

Virulence Factor

Any molecule or characteristic structurally possessed by a pathogen that enhances its ability to cause disease.

Adhesin

A surface protein or structure on a pathogen that allows it to bind specifically to host cell receptors.

Antigenic Variation

The mechanism by which a pathogen alters its surface proteins to evade a host's immune response.

Biofilm

A structured community of bacterial cells enclosed in a self-produced matrix that resists host defenses and antibiotics.

Innate Immunity

The non-specific, non-adaptive component of the immune system that responds identically to all pathogens.

Physical Barrier

A structural blockage, such as intact skin or mucous membranes, that prevents the entry of pathogens.

Chemical Barrier

Secretions like stomach acid or lysozymes that destroy or inhibit pathogens before they penetrate body tissues.

Mucociliary Escalator

Coordinated beating of respiratory cilia to propel mucus-trapped pathogens up and out of the airways.

Phagocytosis

The cellular process where macrophages or neutrophils engulf, digest, and destroy foreign pathogens.

Inflammation

A localized tissue response to damage characterized by swelling, redness, heat, and pain, mediated by histamine.

Histamine

A chemical signal released by mast cells causing vasodilation and increased capillary permeability.

Vasodilation

The widening of blood vessels to increase localized blood flow and deliver white blood cells to an infection site.

Complement System

A group of blood plasma proteins that amplify inflammation, tag pathogens, and rupture bacterial membranes.

Fever

A systemic increase in body temperature driven by pyrogens to slow pathogen replication and accelerate immune metabolism.

Adaptive Immunity

The highly specific, memory-forming branch of the immune system that targets distinct antigens.

Antigen

Any foreign molecule, typically a protein or polysaccharide, that triggers an immune response.

Humoral Immunity

The antibody-mediated immune response driven by B-lymphocytes targeting extracellular pathogens.

B-Lymphocyte

A white blood cell matured in the bone marrow that differentiates into antibody-secreting plasma cells.

Plasma Cell

A short-lived, specialized cell derived from B-cells that synthesizes and secretes large quantities of antibodies.

Memory Cell

A long-lived lymphocyte that persists in the body to provide rapid, robust immunity upon subsequent reinfection.

Antibody

A Y-shaped protein produced by plasma cells that binds specifically to a corresponding antigen to neutralize or clump it.

Cell-Mediated Immunity

The T-lymphocyte-driven immune response that eliminates infected, abnormal, or cancerous host cells.

T-Lymphocyte

A white blood cell matured in the thymus that coordinates the immune system or destroys infected cells.

Helper T-Cell

A regulatory T-cell that secretes cytokines to activate both B-lymphocytes and cytotoxic T-lymphocytes.

Cytotoxic T-Cell

A killer T-cell that recognizes foreign antigens on host cell surfaces and destroys those cells using perforins.