Unit 1: Principles of Epidemiology Flashcards
How is the term “host “defined?
As a living person or animal that is harboring a disease agent
How is the term “carrier” defined?
As a person or animal that harbors a disease agent but has no clinical signs of the disease
How is a primary (definitive) host defined as?
Agent attains its maturity and goes through its sexual or reproductive stage
How is a secondary (intermediate) host defined as?
Agent is in its larval stages
What are infectious disease agents?
Organisms that live on or in the body of a host and can produce disease or illness
What is infectivity?
The ability of the agent to invade and multiply, or to produce infection in the host
What is pathogenicity?
The ability of an agent to produce clinical disease in a host
What is virulence?
The proportion of clinical cases resulting in severe clinical manifestations
Which agent type are multicellular organisms, often referred to as parasites and are capable of causing disease in both animals and humans?
Metazoa
Which agent type are single-celled, animal-like organisms? Most are free-living and found in soil and water.
Protozoa
What are the two forms of fungi?
Single cell (yeast)
Multicellular (molds)
What are the three shapes bacteria can be found in?
Bacillus (rod)
Coccus (sphere)
Spirillum (spiral)
Which agent type are small bacteria, obligate, and intracellular parasites?
Rickettsia
Which agent type are particles of nucleic acid, highly infectious, and cause common diseases?
Viruses
When a host is exposed to a disease agent, what are the three possible outcomes?
- Nowhere to lodge—agent unable to penetrate a host’s body or unable to stay in host’s body
- No effect—agent may enter a host’s body but not cause signs and symptoms
- Great effect—agent may invade a host’s body, multiply, and cause signs and symptoms of disease
What are the three main modes of entry used by disease agents to enter the body?
Ingestion
Inhalation
Penetration
What are the three parts to a chain of infection?
Source or reservoir, mode of transmission, and a susceptible person or host
What may serve as a source of infection?
Person
Animal
Inanimate object
Substance
What are the two ways direct transmission can occur?
Direct contact
Contact with droplets
What are the three ways indirect transmission can occur?
Vehicleborne
Vectorborne
Airborne transmission
What are the two categories under vectorborne transmission?
Mechanical
Biological
What term is used to describe a person who is actually ill with a disease?
Case
What term is used to describe a person who harbors disease organisms, but is not ill?
Carrier
What is the most effective way to prevent and/or control disease?
Break the chain of infection
What are the measures to control or prevent infection at the source?
Diagnosis and treatment
Isolation
Destruction of the source
Education
How does the skin and mucous membranes protect the body?
By providing a protective covering against living organisms and many chemicals
What are three protective structures that help the body against physical forces and aid in thermal regulation?
Hair
Sweat glands
Fat pads
How is the abdominal cavity designed to protect the vital organs?
It is well lubricated so the organs will slide out of line with direct pressure and sharp objects
How does the respiratory tract protect itself?
When coughing or sneezing is initiated, and with the cilia’s constant beating to remove harmful substances
In what functional ways does the gastrointestinal tract protect the body?
By initiating vomiting and diarrhea to move unwanted objects out of the system
How does the body defend itself against living pathogens?
White blood cells attack and destroy pathogens at a site, causing inflammation, and are moved to the lymphatic system
How does the age of a population affect the occurrence of disease?
The very young have poorly developed immune systems, while the very old have defense systems that are starting to weaken
What are the three gender factors affecting the distribution of disease?
Anatomical differences
Hormonal factors
Exposure potential
What effect does an inadequate intake of nutrients have on the body?
There is less energy that can be used to produce antibodies and white blood cells
What effect does stress have on host defenses?
It does not allow the body’s defense system to work at its fullest