Introduction to Infectious Diseases: Terms and Concepts

Vocabulary flashcards covering core terms, classifications of disease, types of pathogens, carrier states, and stages of infectious disease from the lecture notes.

Etiology

The study of the cause of disease.

Etiological agent

The pathogen associated with a particular disease.

Ecological niche

The habitat in which a species lives.

Infection

The multiplication of organisms in an individual or a population.

Disease

A disorder of structure or function in the host that adversely impacts the host and is not simply a result of physical injury.

Infectious Diseases

Diseases caused by pathogenic microorganisms such as bacteria, viruses, parasites, fungi, or prions.

Microbiome

Microbiota built by a diverse collection of fungi, bacteria, archaea, viruses, and mites that covers many animal tissues.

Commensal microorganisms

Microorganisms that are fundamental for maintaining a healthy microbiome by preventing the colonization of harmful pathogens.

Communicable disease

Any infectious disease that spreads from individual to individual, which may require a specific mode of transmission (e.g., vector transmission, sexual transmission).

Contagious disease

Infectious diseases that spread easily from an individual to another individual by air or physical touch.

Notifiable disease

A disease legally mandated to be reported to public health authorities to enable surveillance, outbreak detection, public health response, and controlling or preventing disease spread.

Reportable disease

A broader term referring to state-regulated diseases that must be reported to relevant authorities for tracking and monitoring.

Free-living organism

An organism whose ecological niche is outside the animal body.

Commensal organism

A microorganism that is a normal inhabitant of the animal body, where neither party is harmed under normal circumstances.

Pathogen

A microorganism capable of causing disease, including commensals and non-commensals.

Facultative pathogen

A microorganism that can live outside the host (free-living or commensal) and multiply in the environment, but can also infect, multiply in, and occasionally cause disease in hosts.

Opportunistic pathogen

A microorganism (commensal or free-living) that causes disease only when the host's defenses are compromised (e.g., immunosuppression, wounds, microbiota disruption).

Obligate pathogen

A microorganism that must produce disease (damage at a molecular level) to transmit and thereby survive evolutionarily.

Zoonotic pathogen

A microorganism that is a commensal or pathogen on animals but can be transmitted to humans and cause disease via vectors or direct contact.

Incubatory carrier

A host that is incubating the pathogen but is not yet ill, though it may shed the pathogen.

Convalescent carrier

A host that is recovering with no clinical signs, but continues to harbor and potentially transmit the pathogen to others.

Active (persistent) carrier

An animal that recovered from the disease but could not eradicate the pathogen and continuously sheds it into the environment.

Latent (persistent) carrier

A host that harbors the pathogen internally and typically sheds it only intermittently, often triggered by stress or immunosuppression.

Subclinical carrier

An animal infected with a pathogen that does not exhibit clinical signs of disease, but can still shed the pathogen and contribute to transmission.

Clinical carrier

An infectious animal with a clinical infection in a peracute, acute, or chronic phase.

Incubation period

The first stage of an infectious disease in which the pathogen multiplies without clinical signs.

Prodromal stage

The second stage of an infectious disease characterized by general and unspecific signs.

Illness stage

The third stage of an infectious disease in which clinical signs and symptoms are more severe and specific.

Decline stage

The fourth stage of an infectious disease where the number of pathogens and clinical signs begin to decrease.

Convalescence stage

The fifth and final stage of an infectious disease characterized by the host returning to a healthy state.