11. Characteristics of Infectious Disease and Pathogens (Vocabulary)

Vocabulary flashcards covering key terms from infection, disease, pathogenesis, and virulence factors across bacteria, viruses, fungi, protozoa, and helminths.

Infection

Entry and multiplication of a microorganism within a host.

Disease

Any deviation from the normal function or structure of the host.

Signs

Objective, measurable indicators of disease.

Symptoms

Subjective experiences of disease reported by the patient.

Noninfectious disease

Disease caused by genetics or environment, not pathogens.

Infectious disease

Disease caused by pathogens such as bacteria, viruses, or fungi.

Communicable

Capable of being transmitted from one host to another.

Contagious

Easily transmitted between individuals.

Noncommunicable disease

Disease not typically spread between people, but may be linked to environmental reservoirs or zoonoses.

Zoonoses

Diseases that can be transmitted from animals to humans.

Nosocomial infection

Infection acquired in a hospital or health care setting.

Iatrogenic disease

Disease directly resulting from a medical procedure or treatment.

Acute disease

Disease of short duration.

Chronic disease

Disease lasting months or years.

Latent disease

Disease with years-long dormancy where there is no active replication.

Incubation period

Time between exposure and the first signs or symptoms.

Prodromal period

Early, nonspecific symptoms before full illness develops.

Period of illness

Phase with peak signs and symptoms of disease.

Period of decline

Phase during which signs and symptoms lessen.

Period of convalescence

Recovery period after illness resolves.

Koch’s postulates

Criteria to determine if a microorganism causes a disease.

Molecular Koch’s postulates

Genetic criteria to identify genes contributing to pathogenicity.

Virulence

Degree to which a pathogen can cause disease.

ID50

Infectious dose required to infect 50% of an exposed population.

LD50

Lethal dose required to kill 50% of a population.

Primary pathogen

Pathogen that can cause disease in a healthy individual.

Opportunistic pathogen

Pathogen that causes disease when host defenses are compromised.

Environmental pathogen

Pathogen that can be acquired from the environment.

Resident microbiota

Microbes that normally inhabit the host without causing disease.

Local infection

Infection confined to a single region or tissue.

Focal infection

Infection that spreads from a local site to other parts of the body.

Systemic infection

Infection that disseminates through the bloodstream to multiple body sites.

Secondary infection

Infection that follows and is facilitated by prior infection or antimicrobial treatment.

Portals of entry

Routes by which pathogens enter the body.

Portals of exit

Routes by which pathogens leave the host to spread to others.

Exposure

Stage of pathogenesis where the host first encounters the pathogen.

Adhesion

Attachment of the pathogen to host cells.

Invasion

Spread of the pathogen into host tissues.

Infection (pathogenesis stage)

Colonization and growth of a pathogen within the host.

Transmission

Spread of pathogens from an infected host to new hosts.

Virulence factors

Molecules that enhance a pathogen’s ability to cause disease.

Exoenzymes

Enzymes secreted by pathogens that help invade tissues.

Toxins

Substances that cause tissue damage or disease symptoms.

Exotoxins

Toxins secreted by bacteria into the surrounding environment.

Endotoxin

Lipid A component of the outer membrane LPS in gram-negative bacteria.

Lipid A

Lipid component of endotoxin responsible for toxicity.

Capsule

Polysaccharide layer that protects bacteria from phagocytosis.

Antigenic variation

Changes in surface antigens to evade immune detection.

Adhesins

Molecules on pathogens that promote attachment to host cells.

Antigenic drift

Gradual changes in viral antigens, altering immune recognition.

Antigenic shift

Major, abrupt change in viral antigens leading to new strains.

Influenza antigenic drift and shift

Flu viruses utilize both drift (gradual) and shift (sudden) to evade immunity.

Fungal virulence factors

Fungal mechanisms such as adhesins, toxins, exoenzymes, and capsules aiding infection.

Protozoan adhesins

Adhesive molecules used by protozoa to attach to host cells.

Cytopathic substances

Factors produced by protozoa that damage host cells.

Antigenic variation in protozoa

Change in surface antigens to avoid immune responses.

Capsules in protozoa

Capsules that protect protozoa from phagocytosis.

Helminthic immune evasion

Coating with host-like glycans or immune suppression to avoid defenses.

Glycan camouflage

Glycan molecules on helminths that mimic host cells to evade immunity.

Immune suppression by helminths

Helminths can dampen the host immune response to persist infections.