General Principles of EPI

Question 1

Describe EPI

Answer 1

Study of the
Frequency
distribution
cause
control of disease in populations

Understand the relationship between host, environment and organism

Question 2

Purpose of EPI

Answer 2

Person, place, and natural history

Question 3

Define Risk

Answer 3

Probability or likelihood of an event occuring

Question 4

Define Risk Factor

Answer 4

Characteristic, behavior, experience that increases the probability of developing a negative health status (disease or infection).

Question 5

Epidemiology, unlike clinical medicine, is population based and is useful for describing health-related phenomena in groups of people.

Question 6

Epi triangle model of disease causation

Answer 6

Host: human or other animal
Environment: external factors associated with the host
Agent: bacteria, virus, fungus, protozoan, helminth or prion

Question 7

Wheel model

Answer 7

Hub: host or human with an inner core of genetic information.
Surrounding environment divided into three parts: social, biological, physical.

Question 8

Web Model of causation

Answer 8

aims to capture the more complex interactions between biological (host), environmental, and social factors contributing to disease.

Emphasizes social and political aspects of human life.

Question 9

What is an association and the three types?

Answer 9

As one variable changes there is a resultant change in the quantity or quality of another variable.

Artifactual (spurious) (chance or random error)- may be result of study design-> systematic error or bias.
Indirect or noncausal-> may result from mixing of effects between the exposure, the disease, and a third factor (confounding variable)
Casual

Question 10

What is a confounding variable?

Answer 10

Related to both the potential cause of a disease and the disease itself.

Question 11

Scientific criteria for CAUSATION (Koch) 4 points

Answer 11

1. organism must always be found with the disease, in accordance with the clinical stage observed
2. the organism must then be grown in pure culture from a diseased host
3. the same disease must be reproduced when a healthy susceptible host is innoculated
4. the organism must be recovered from the experimentally infected host.

Question 12

Hill’s Criteria for Caustion

Applying the criteria for causality is not as straightforward when the etiology is not clear

Answer 12

1. Strength of association
2. Consistency
3. Specificity
4. Temporality
5. Biological Gradient
6. Biologically Plausible
7. Coherence
8. Experimental Knowledge
9. Analogy

Question 13

HAI prevention strategies are wide ranging and depend on the disease in question and what information is available to the practitioner.

Primary, secondary and tertiary prevention

Answer 13

Primary prevention strategies to prevent the occurrence of disease include: barrier precautions, immunizations of HCP, cleaning, sterilizing, and disinfecting.

Question 14

Define incidence

Answer 14

Number of new cases of a given disease in a given time period

Question 15

Define prevalence

Answer 15

number of existent cases of a given disease at a given time.

Question 16

Endemic

Answer 16

usual incidence of a given disease within a geographical area during a specified time period

Question 17

Epidemic

Answer 17

an excess over the expected incidence within a geographical area during a specified time period

Question 18

Pandemic

Answer 18

Epidemic spread over a wide geographic area, across countries or continents

Question 19

Outbreak

Answer 19

A group of people with the same disease who are epidemiologically linked

Question 20

Cluster

Answer 20

a group of persons with a given disease occurring in the same space and time, but which have not been epidemiologically linked. If linked, by EPI may become an outbreak.

Question 21

Zoonosis

Answer 21

A disease transmitted from animals to humans

Question 22

Enzootic

Answer 22

Usual presence of disease among animals within a geographical area. Animals may serve as a reservoir.

Question 23

Epizootic

Answer 23

excess of disease than in expected in the animal population

Question 24

Reservoir

Answer 24

Place where agent can survive but may or may not reproduce.

Eg. Pseudomonas (gram negative, arerobic rod) in nebulizers
Hep b on surface of hemodialysis machine

Question 25

Fomite

Answer 25

inanimate object on which organisms may exist for some period of time

Question 26

Herd immunity

Answer 26

resistance of a group to invasion and to spread of infectious agent

Question 27

Convalescent carriers

Answer 27

those who have recovered from the disease but still have organisms present that can be transmitted.

Eg. a patient with cholera may continue to shed bacteria in the stool for several weeks after diarrhea has subsided.

Question 28

Natural barriers to the entry of organisms include:

Answer 28

1. skin and mucous membranes
2. cilia of respiratory tract and cough mechanism
3. gastric acid
4. mechanical flushing - genitourinary tract
5. tear flushing- protect the eye
6. good nutritional status

Question 29

Host factors influencing susceptibility include:

Answer 29

Age, sex, ethnicity, SES, martial status, lifestyle, heredity, nutritional status, occupation, immunization status, diagnostic/therapeutic procedures, Medications, pregnancy, trauma

Question 30

Describe prospective or cohort studies

Answer 30

A group of subjects with a known exposure status for the risk factor of interest are followed over time to determine which of the subjects develops disease.

Subjects form a cohort going through time together.

Question 31

Describe Case control- or retrospective

Answer 31

Moving backward from disease state to risk factor. identify those with disease then measure degree of exposure to the risk factor of interest.

Question 32

Pros and cons of case control

Answer 32

Pros
data is already available. Researcher doesn’t have to wait for disease to develop- takes less time. Tend to be less expensive.
Cons
dependent on completeness of records, may be difficult to select an appropriate control group. Subject or recall bias- rely on memory of subjects.

Question 33

Pros and cons of Cohort

Answer 33

Pros
Considered to have fewer bias- avoid subjectivity involved in collecting after the fact exposure data.
Yield incidence rates- can yield associations between risk factors and disease that were not anticipated.
Tend to carry more weight
Cons
May require lengthy follow up- more expensive. Must wait for sufficient number to develop disease. May have people drop out.

Question 34

Recognizing outcome related events:

Answer 34

decreased rates of infection, length of stay, days in ICU,

Question 35

Histogram

Answer 35

graphic of frequency distribution in which one bar is used for each time interval, and there is no space between the intervals

Question 36

Frequency polygon

Answer 36

provides same info as a histogram

Question 37

A CHART is a method of illustrating info using only one coordinate. They compare magnitudes of different events and to compare parts of a total picture.

Types of charts include:

Answer 37

Bar charts, pictograms, geographical coordinate charts, and pie charts.

Question 38

Bar charts and pictograms

Answer 38

Used to compare magnitudes, show frequency distributions, and time-series data.

Question 39

Geographical Coordinate Charts

Answer 39

Represent the occurrence of events using maps.

Question 40

Pie charts

Answer 40

a pie chart is not appropriate when there are may wedges- limit the number to five or six.

Question 41

U-Charts: Provide statistical process control (SPC) information to help monitor quality assurance and are most often used for monitoring length of stay and infection rates.

Answer 41

Provides a range of expected variation about a mean (centerline) and the upper and lower limits beyond which the process is considered out of control.
Useful in conveying changes in rates over time and identifying points in time when infection rates or other processes are outside the expected range.
In can include more than one error (infection) per patient. May be less stable with small denominators.