Epidemiology Lecture 1: Infectious Disease Application Flashcards
What are the basic tenets of epidemiology?
- Concept of time-space clustering
- The epidemiologic triad
- Host factors
- Agents of disease
- Environmental factors
What is epidemiology?
Study of occurrence, spread, and control of disease in population and is the basic science and most fundamental practice of public health and preventative medicine
What is the concept of time-space clustering?
- Distribution of disease occurs in patterns
- Patterns of disease in communities are predictable
- Pattern characteristics of disease may suggest or lead to measures to control/prevent disease
What is the epidemiologic triad?
- States in order for disease to occur, must be unique combination of events
- Triangle includes host, environment, and agent
- Disease can be blocked by intersecting triangle
Define vector and vehicle
- Vector: Environmental character that carries the agent ie. arthropod (insect)
- Vehicle: carries the vector ie. water
What are host factors and some examples?
- Determine disease occurrence include biological traits which the host is born, and social traits which the host acquires
- Biological traits: genetics, race, ethnicity, sex, and age
- Social traits: behavior and nutrition ie. marriage, life-style
What are agents of disease?
- Biologic: microorganisms
- Chemical: toxins or poisons
- Nutritional: excess of food, lack of food, or vitamin deficiency
- Physical forces: automobiles
- Energy: ionizing radiation
What is pathogenicity?
Ability to produce disease in a host organism
Define virulence and virulence factors
- Degree of pathogenicity
2. Factors include pathogen’s genetic, biochemical, or structural features that enable it to produce disease
What are measures of virulence?
Lethal dose of 50%
Infectious dose of 50%
What are horizontal and vertical routes of agent transmission?
- Horizontal: zoonoses (animal), vectors, ingestion, aerosol, fomites, direct contact, or parenteral (blood borne)
- Vertical: mother-to-child, transplacental/perinatal
What is herd immunity?
Spread of a disease within a group based on proportions of susceptible and immune individuals in a group. Outbreaks more likely with more susceptible than immune in population.
What are environmental factors?
- Physical
- Biologic
- Social
What are physical factors?
- Climate: temperature and moisture
- Setting: urban/rural
- Gravity
- Pollution: water and air
- Presence of vectors and reservoir
What are mechanical and biological vectors?
- Mechanical: eg. Fly is a vector that physically carries agent
- Biological: eg. Ticks, vector in which agent replicates, is a reservoir
What is a reservoir?
Habitat where agent thrives, propagates, and multiply rapidly ie. humans, soil, water, animals, insects, or plants
Define endemic
Human disease present in a particular region in an essentially constant level (expected incidence)
Define epidemic and types of epidemic
Sudden increase of incidence of a particular disease above the expected incidence
- Common source
- Point source: exposed to pathogen at one point in time (food poisoning)
- Propagative (progressive): serial transmission
Define pandemic
Applied to epidemics of unusually large proportions (worldwide)
Define Zoonosis
A disease of animals transmissible directly to humans
Define Enzootic
A disease of animals present in a particular region at an essentially constant level
Define Epizootic
A sudden increase in the incidence of a particular disease in the animal population
Define infection
Presence of microorganisms in or on host tissues
Define primary prevention
Used before person gets disease. Aims to prevent disease from occurring. Primary prevention reduces both incidence and prevalence of disease
Define secondary prevention
Used after disease has occurred, but before person notices that something is wrong. Find symptoms and treat disease early
Define Tertiary prevention
Used on person who already has symptoms of disease.
- Prevent damage and pain
- Slow disease
- Prevent complications
- Provide better care
- Make infected healthy/functional
Define incidence
Number of new cases reported during a specific time period. Tells rate of disease traveling in specific population.
What is the equation for incidence rate?
Incidence rates = # of new cases in pop. in time period / # of persons at risk
