Infectious Disease

This set of flashcards covers essential vocabulary and concepts related to infectious diseases, including definitions and explanations of key terms.

Microbiome

A community of microorganisms living together in a particular environment, including the human body.

Symbiotic

A close relationship between two organisms of different species.

Commensalism

A type of symbiotic relationship where one organism benefits while the other is neither helped nor harmed.

Mutualism

A type of symbiotic relationship where both organisms benefit.

Parasitism

A type of symbiotic relationship where one organism benefits at the expense of the other.

Resident microbiota

Microorganisms that are permanently colonized in a particular habitat of the body.

Transient microbiota

Microorganisms that are temporarily present in a particular habitat.

Opportunistic pathogen

A microorganism that normally does not cause disease but can become pathogenic under certain conditions.

Contamination

The presence of a harmful agent on a surface or in a substance.

Infection

The invasion and multiplication of pathogenic microorganisms in the body.

Disease

An impairment of bodily functions resulting from infection or other causes.

Symptoms

Subjective evidence of disease reported by the patient.

Signs

Objective evidence of disease that can be observed or measured.

Reservoir

The natural habitat of a pathogen where it lives and multiplies.

Zoonoses

Diseases that can be transmitted from animals to humans.

Carrier

A person or organism that harbors a pathogen but does not exhibit symptoms.

Transmission

The mechanism by which an infectious agent is spread.

Healthcare-associated infection

An infection acquired during the course of receiving healthcare treatment.

Superinfection

An infection occurring during or following treatment for another infection.

Epidemiology

The study of how diseases are distributed in populations and the factors that influence them.

Etiology

The study of the cause of a disease.

Pathogenicity

The ability of a microorganism to cause disease.

Virulence

The degree of pathogenicity of a microbe, often measured by the severity of the disease it causes.

How is microbiome established ?

Through birth, diet, environment, and contact with others

How can normal microbiota cause disease?

If they move to a sterile site, the immune system is weakened, or they grow uncontrollably.

Why doesn’t contamination always lead to infection?

The immune system may remove the contaminant or it may not reach a suitable environment

What are the stages of infectious disease?

Incubation → Prodromal → Illness → Decline → Convalescence.

Incubation

The time between the entry of the pathogen into the body and the appearance of the first symptoms. The person may not know they’re infected, but the pathogen is multiplying.

Prodromal

A short phase where early, mild symptoms appear (like fatigue, muscle aches, or a general “unwell” feeling) before the illness becomes more severe.

Illness

The period when the disease is most severe, and symptoms are most intense. The immune system is actively fighting the pathogen during this stage.

Decline

The stage where symptoms begin to subside as the immune system or treatment successfully reduces the number of pathogens. The patient starts to feel better.

Convalescence

The final stage where the patient recovers, tissues are repaired, and body functions return to normal. The person may still be contagious during this time.

Which body systems have microbiota and vary by abundance/type?

Respiratory tract, digestive tract, urogenital tract, skin/eyes.

What are the three main reservoirs of infection?

Humans, animals (zoonoses), and non-living (soil, water).

What are common portals of entry/exit for pathogens?

Skin, mucous membranes, respiratory tract, urogenital tract, placenta.

What are the 3 modes of transmission?

Contact (direct/indirect), vehicle (air, water, food), vector (biological/mechanical).

What is the difference between droplet and airborne transmission?

Droplet = short-range (e.g., coughing); Airborne = travels long distances (e.g.,

Where do pathogens in HAIs come from?

Exogenous (external), endogenous (patient’s own microbiota), iatrogenic (caused by medical procedure)

What is the #1 way to reduce healthcare-associated infections?

Proper hand hygiene.

How do we track disease?

By frequency, geography, and pattern (e.g., outbreaks, epidemics).

How do pathogens adhere to host cells?

Using adhesion molecules like fimbriae, capsules, or proteins.

What are secreted virulence compounds?

Enzymes and toxins (e.g., hemolysins, leukocidins).

What are antiphagocytic factors?

Factors that help pathogens avoid being engulfed by phagocytes (e.g., capsules, protein A).

What are the types of epidemiological studies?

Describe the compounds infectious agents secrete (enzymes, toxins) and how these can influence their virulence?

What compounds do infectious agents secrete (enzymes, toxins), and how do these influence virulence?