Epidemiology Lecture 1: Infectious Disease Application

Question 0

What are the basic tenets of epidemiology?

Answer 0

1. Concept of time-space clustering
2. The epidemiologic triad
3. Host factors
4. Agents of disease
5. Environmental factors

Question 1

What is epidemiology?

Answer 1

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

Question 2

What is the concept of time-space clustering?

Answer 2

1. Distribution of disease occurs in patterns
2. Patterns of disease in communities are predictable
3. Pattern characteristics of disease may suggest or lead to measures to control/prevent disease

Question 3

What is the epidemiologic triad?

Answer 3

1. States in order for disease to occur, must be unique combination of events
2. Triangle includes host, environment, and agent
3. Disease can be blocked by intersecting triangle

Question 4

Define vector and vehicle

Answer 4

1. Vector: Environmental character that carries the agent ie. arthropod (insect)
2. Vehicle: carries the vector ie. water

Question 5

What are host factors and some examples?

Answer 5

1. Determine disease occurrence include biological traits which the host is born, and social traits which the host acquires
2. Biological traits: genetics, race, ethnicity, sex, and age
3. Social traits: behavior and nutrition ie. marriage, life-style

Question 6

What are agents of disease?

Answer 6

1. Biologic: microorganisms
2. Chemical: toxins or poisons
3. Nutritional: excess of food, lack of food, or vitamin deficiency
4. Physical forces: automobiles
5. Energy: ionizing radiation

Question 7

What is pathogenicity?

Answer 7

Ability to produce disease in a host organism

Question 8

Define virulence and virulence factors

Answer 8

1. Degree of pathogenicity

2. Factors include pathogen’s genetic, biochemical, or structural features that enable it to produce disease

Question 9

What are measures of virulence?

Answer 9

Lethal dose of 50%

Infectious dose of 50%

Question 10

What are horizontal and vertical routes of agent transmission?

Answer 10

1. Horizontal: zoonoses (animal), vectors, ingestion, aerosol, fomites, direct contact, or parenteral (blood borne)
2. Vertical: mother-to-child, transplacental/perinatal

Question 11

What is herd immunity?

Answer 11

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.

Question 12

What are environmental factors?

Answer 12

1. Physical
2. Biologic
3. Social

Question 13

What are physical factors?

Answer 13

1. Climate: temperature and moisture
2. Setting: urban/rural
3. Gravity
4. Pollution: water and air
5. Presence of vectors and reservoir

Question 14

What are mechanical and biological vectors?

Answer 14

1. Mechanical: eg. Fly is a vector that physically carries agent
2. Biological: eg. Ticks, vector in which agent replicates, is a reservoir

Question 15

What is a reservoir?

Answer 15

Habitat where agent thrives, propagates, and multiply rapidly ie. humans, soil, water, animals, insects, or plants

Question 16

Define endemic

Answer 16

Human disease present in a particular region in an essentially constant level (expected incidence)

Question 17

Define epidemic and types of epidemic

Answer 17

Sudden increase of incidence of a particular disease above the expected incidence

1. Common source
2. Point source: exposed to pathogen at one point in time (food poisoning)
3. Propagative (progressive): serial transmission

Question 18

Define pandemic

Answer 18

Applied to epidemics of unusually large proportions (worldwide)

Question 19

Define Zoonosis

Answer 19

A disease of animals transmissible directly to humans

Question 20

Define Enzootic

Answer 20

A disease of animals present in a particular region at an essentially constant level

Question 21

Define Epizootic

Answer 21

A sudden increase in the incidence of a particular disease in the animal population

Question 22

Define infection

Answer 22

Presence of microorganisms in or on host tissues

Question 23

Define primary prevention

Answer 23

Used before person gets disease. Aims to prevent disease from occurring. Primary prevention reduces both incidence and prevalence of disease

Question 24

Define secondary prevention

Answer 24

Used after disease has occurred, but before person notices that something is wrong. Find symptoms and treat disease early

Question 25

Define Tertiary prevention

Answer 25

Used on person who already has symptoms of disease.

1. Prevent damage and pain
2. Slow disease
3. Prevent complications
4. Provide better care
5. Make infected healthy/functional

Question 26

Define incidence

Answer 26

Number of new cases reported during a specific time period. Tells rate of disease traveling in specific population.

Question 27

What is the equation for incidence rate?

Answer 27

Incidence rates = # of new cases in pop. in time period / # of persons at risk