Week 1 - Principles of Control of Infectious Disease

Pathogenicity

extent to which clinically manifest disease is produced in an infected population

(symptoms of those infected)

High: measies, rabies, smallpox, SARS-CoV-1

Low: Polio, TB, SARS-CoV-2

Virulence

The extent to which severe disease is produced in a population with clinically manifest disease

High: rabies, ebola, smallpox

Low: rubella, mumps, rhinovirus

Invasiveness

ability to invade tissues

Intoxication

ability to produce toxins

Allergenicity

Ability to cause damaging hypersensitivity reactions

Antigenic Variability

ability to undergo antigenic variation

Antibiotic or antiviral resistance

ability to develop antibiotic (bacteria) or antiviral (viruses) resistance

Infective Dose

the number of organisms needed to cause an infection

Infection

when an infectious agent enters a body and develops and multiplies

Infectious Agents

organisms capable of producing inapparent infection or clinically manifest diseaseIf

Infectious disease

An infection that results in a clinically manifest disease. May also be due to the toxic product of an infectious agent

Control of Infectious Disease

the actions and programs directed toward reducing disease incidence, reducing disease prevalence, or completely eradicating the disease

Primary prevention

control aimed at reducing the incidence of infectious disease

Secondary prevention

control aimed at reducing the prevalence of infectious disease by shortening duration

Tertiary prevention

control aimed at reducing or eliminating long-term impairments of infectious disease

Route of Transmission

the mechanisms by which infectious agents are spread from reservoirs or sources to human hosts

Reservoir

any person, other living organism or inanimate material in which infectious agents normally lives and growsSo

Source

the person, other living organism or inanimate material from which the infectious disease came from

Direct Transmission

direct and essentially immediate transfer of infectious agents to a receptive portal of entry through which human or animal infection may take place

ex: touching, biting, projecting, sexual contact

Indirect Transmission - Vector-borne

contaminated inanimate materials or objects

ex: toys, water, food, clothes

Indirect Transmission - Mechanical

Includes simple mechanical carriage by a crawling or flying insect or by passage of organisms. Does NOT require multiplication or development of the organism

Indirect Transmission - Biological

Transmission by material capable of penetrating the skin

ex: injection of salivary gland when biting, regurgitation, feces

Indirect Transmission - Airborne

dissemination of microbial aerosols to a suitable portal of entry from the air

Airborne Transmission - Droplets

small residues which result from evaporation of fluid from droplets emitted by an infected host

Airborne Transmission - Dust

small particles of widely varying size from soil, clothes, bedding, floors, etc

HOST - Chain of Infection

Respiratory tract

Intact skin

Gastrointestinal tract

Mucous membranes

Urinary tract

Placenta

Mechanisms that get past the body’s natural barriers

HOST - Host factors

most important regarding developing clinically manifest disease and the severity are immune status and age

HOST - Nonspecific Defense Mechanisms

includes the intact skin, nasal cilia, tears, saliva, mucus, and gastric acid

HOST - Specific Defense Mechanisms

naturally acquired immunity from previous infection, passive immunity in the newborn from the mother, and artificial passive immunity from immunoglobulins and antitoxins