Infectious Disease, Pathogens, Transmission, and Immunity Flashcards

Vocabulary flashcards covering infectious vs non-infectious disease, pathogen entry and replication, modes of transmission, disease control methods, innate and adaptive immune responses, and vaccination strategies.

Non-infectious Disease

A non-communicable disease that is not caused by pathogens and often results from genetics, lifestyle, or environmental factors.

Infectious Disease

A communicable disease caused by transmissible pathogens such as bacteria, viruses, fungi, or parasites.

Pathogen

Any organism or agent that lives on or in a host and causes disease.

Adhesins

Specific molecules on the outer surface of pathogens that bind to complementary receptor proteins on host cell surfaces to enable attachment.

Receptor-Mediated Endocytosis

A pathogen entry mechanism where host cell surface receptors bind to pathogen proteins, leading to cell membrane invagination and engulfment into a vesicle.

Binary Fission

An asexual reproduction method used by bacterial pathogens where a single bacterium divides into two genetically identical daughter cells.

Antigenic Variation

A strategy used by pathogens like Plasmodium to alter their surface proteins and evade recognition by host antibodies.

Rosetting

The clumping of infected red blood cells around uninfected red blood cells, which shields infected cells from host immune cells.

Direct Transmission

The direct transfer of a pathogen from an infected host to a new host without any intermediate non-living object or living organism.

Droplet Transmission

Direct contact transfer of pathogens via large respiratory droplets released by coughing or sneezing over short distances of $3\text{ to }6\text{ feet}$.

Airborne Transmission

Indirect transmission where pathogens remain suspended in the air inside tiny aerosol droplets that stay airborne longer and travel further than large droplets.

Fomites

Non-living contaminated surfaces or objects, such as doorknobs or towels, that transmit pathogens to a new host.

Vector Transmission

Transmission of a pathogen via a living organism (such as a mosquito, tick, or flea) that actively carries and transfers the pathogen between hosts.

Yersinia pestis

The bacterium responsible for causing the Bubonic Plague, transmitted by rodent fleas with the Black Rat acting as its reservoir host.

Antibiotics

Internal prescribed medicines used to kill or inhibit the growth of bacteria inside the body.

Antiseptics

Chemical agents applied to living tissue or skin to kill or inhibit microorganisms.

Disinfectants

Strong chemical agents applied to non-living surfaces to eliminate a broad range of microorganisms.

Lysozyme

An enzyme present in body secretions like tears, saliva, and urine that breaks down bacterial cell walls.

Innate Immune Response

A rapid, non-specific defense system present from birth that acts immediately against foreign invaders without providing long-term memory.

Complement System

A group of liver-produced blood proteins that enhance immunity through membrane attack complex formation, opsonisation, and chemotaxis.

Membrane Attack Complex (MAC)

A protein structure formed by the complement system on pathogen membranes that creates pores, causing fluid influx and cell lysis.

Opsonisation

The process of coating or tagging pathogens with molecules such as complement proteins or antibodies to facilitate recognition by phagocytes.

Phagocytosis

The cellular process where phagocytes (like neutrophils and macrophages) engulf pathogens into a vesicle (phagosome) to break them down with lysosomal enzymes.

Histamine

A chemical released by mast cells and basophils that causes blood vessel dilation and increased permeability during an inflammatory response.

Natural Killer (NK) Cells

Cytotoxic innate lymphocytes that recognize stressed, cancerous, or virus-infected cells and induce apoptosis using perforins and granzymes.

Antigen

A foreign 'not-self' particle or protein structure on a pathogen's surface that stimulates an immune response.

Antibody

A Y-shaped protein produced by plasma B cells that specifically binds to a complementary target antigen on a pathogen.

Agglutination

The clumping together of pathogens caused by antibody binding, which restricts pathogen movement and increases phagocytosis efficiency.

Helper T Cells

CD4+ T lymphocytes that coordinate the immune response by recognizing presented antigens and releasing cytokines to activate B cells and cytotoxic T cells.

Cytotoxic T Cells

CD8+ T lymphocytes that recognize specific foreign antigens on infected host cells and release enzymes to induce programmed cell death (apoptosis).

Active Immunity

Long-term immunity developed when the body produces its own antibodies and memory cells after exposure to an antigen (naturally or via a vaccine).

Passive Immunity

Short-term immunity gained by receiving external antibodies, providing immediate protection without producing memory cells.

Herd Immunity

Indirect protection provided to non-immune or vulnerable individuals when a high proportion of the population is vaccinated or immune.

Smallpox

The first human infectious disease officially declared globally eradicated by the World Health Organization (WHO) in 1980.

mRNA Vaccines

Vaccines delivering messenger RNA that instructs host cells to produce a specific viral protein (such as the COVID-19 spike protein) to trigger an immune response.