Biomedical Sciences: Infectious Disease Terminology (Lecture 5; Exam 1)

Chain of Infection

1. Reservoir of infectious agent

2. Portal of exit

3. Transmission

4. Portal of entry

5. Susceptible host

Portals of Exit or Entry

• Eyes

• Digestive tract

• Respiratory tract

• Broken skin

• Genitourinary tract

Infection

Colonization by a pathogen or within the body.

• Viral replication: Replication within a host cell

  • ex. SARS-CoV-2 infects lung epithelial cells

Infectious Disease

When a microbial infection prevents the body from functioning normally.

• ex. SARS-Cov infects lung epithelial cells leading to signs and symptoms of COVID-19.

Nosocomial Infection

Infection acquired or occurring in a hospital.

Zoonotic Infection

Infection that normally occurs in animals but can also infect humans.

Etiologic Agent/Causative Agent

The microbe/entity responsible for causing the disease.

Disease

The abnormal condition or set of signs and symptoms experienced by a host.

(A causative is the one that triggers the condition.)

Primary Pathogen

Microbe or virus that causes disease in otherwise healthy individual.

• Host: Entity that is harboring the pathogen.

Opportunistic Pathogen

Causes disease only when the body’s innate or adaptive immune responses are compromised, or when they are introduced into an unusual location.

• i.e. Pseudomonas

• *Becoming more common as we advance medically.

Incubation Period

The time between the introduction of the pathogen to a susceptible host and the onset of signs and symptoms.

Illness: Sign

Objective, observable evidence of an illness or disorder.

• A physical manifestation of a disorder that is apparent to a trained healthcare provider and sometimes to the patient.

Illness: Symptom

Any change in the body or its function that is perceived by the patient; the subjective experience of a disease or disorder.

Prodromal Phase (prodrome)

Period of early, vague symptoms that precedes the classic illness.

• i.e. Malaise - feeling of illness, headache

Convalescence

Stage of recuperation and recovery from the disease.

During incubation and convalescence, there are NO symptomatic signs of the disease, however there may still be organisms present that can be infectious.

Carrier

Individuals that harbor an infectious agent for months or years and continue to spread the pathogen even though they appear healthy.

Localized Infection

Microbe is limited to a small area.

Systemic Infection

Infection is disseminated (spread) throughout the body, can be characterized by similar signs and symptoms from a systemic immune response.

Bacteremia

Bacteria in the blood.

• i.e. Sepsis (septic shock)

“-emia” : means in the blood.

Viremia

Viral particles in the blood.

Toxemia

Toxins are circulating in the blood.

Pathogenic

Able to cause disease.

Virulence

Degree of pathogenicity of an organism, capacity of a pathogen to cause disease in a host.

• Can be quantitated

  • Mean time to appearance of symptoms or death.

  • Measurement of fever, weight loss, etc.

  • Measurement of pathological lesions, effect on cells.

  • Infectious dose

• Cannot be used to compare different pathogens

Virulence Factors

Traits of a microorganism that specifically allow it to cause disease.

• Adherence/Colonization factors

• Toxins

• Secretion systems

• Dissemination factors, tissue degrading enzymes, evasion proteins