Applied Epidemiology

Question 1

Name the 5 steps in investigating diseases

Answer 1

1. Observation and recording of the natural occurrence of diseases
2. Presentation and analysis of the observations
3. Determine the cause of the disease
4. Understand transmission, clinical signs, diagnosis – ‘disease ecology’
5. The efficiency of different techniques to combat disease

Question 2

Define epidemic

Answer 2

A level of disease in a population significantly greater than usual

Question 3

Define endemic

Answer 3

Disease commonly found in, or restricted to a particular region, community or group of people

Question 4

Define infectious disease

Answer 4

A disease due to an infectious agent.
Can be contagious or non-contagious

Question 5

Define a contagious disease

Answer 5

A disease transmitted by direct or indirect contact with a host that is the source of the pathogenic agent

Question 6

Define a communicable disease

Answer 6

A disease who’s causative agent can be transmitted from successive hosts to healthy subjects, from one individual to another

Question 7

Define prevalence

Answer 7

A measure of disease occurrence
The proportion of individuals in a population who have the condition at a specified point in time

Question 8

Define incidence

Answer 8

The number of new health-related events in a defined population within a specified period of time

Question 9

Define morbidity

Answer 9

Any departure, subjective or objective, from a state of physiological or psychological well being.

Question 10

Define mortality

Answer 10

The state of being subject to death.

Question 11

What does R0 mean when talking about disease spread

Answer 11

Basic reproductive number of a disease

Question 12

What is the value of R0 in an endemic disease

Answer 12

R0 < 1

Question 13

When is R0 relevant

Answer 13

R0 is relevant only at the beginning of the spread of disease

Question 14

What is the R number

Answer 14

Reproduction number at any time point during an outbreak

Question 15

Describe a point source/common source epidemic and give examples

Answer 15

Rapid increase in cases
Tight clustering of cases, indicates common exposure
Examples - food poisoning, feed contamination

Question 16

Describe a propagating epidemic and give an example

Answer 16

Slow then a rapid increase in cases
Starts with some initial cases then increases
Example - infectious disease

Question 17

Give the 5 aspects of Hill’s criteria for establishing a cause of disease

Answer 17

Time sequence
Strength of association
Biological gradient
Consistency
Coherence or plausibility

Question 18

Name 3 approaches commonly used to confirm a cause of disease

Answer 18

Structure/shape of the epidemic curve
Case-control studies
Cohort studies

Question 19

What is a case-control study

Answer 19

Compare between cases and non-cases (diseased and non-diseased)
Look retrospectively at the differences in exposure to risk factors (i.e. calf shed, ice cream)

Question 20

What is a cohort study

Answer 20

Look retrospectively or prospectively at individuals exposed and not exposed to risk factors (i.e. calf shed, ice cream) and see if they develop the disease

Question 21

Give the 2 common measures of who is at risk of disease, and name the type of study they are commonly used for

Answer 21

Odds ratio => case-control studies
Relevant risk: risk ratio => cohort studies

Question 22

What is meant by the risk difference (RD) of a disease

Answer 22

Comparison between risk of an outcome in an exposed group versus in the unexposed group (cohort)

Question 23

What is meant by an odds ratio (OR)

Answer 23

Odds of the disease in the exposed group vs. with odds of the disease in the unexposed group

Question 24

What is meant by the relative risk:risk ratio

Answer 24

The ratio of risk of disease in the exposed group to risk of disease in an unexposed group

Question 25

Give examples of tests which sub-type genetic material for pathogen identification

Answer 25

PCR fingerprinting
DNA sequencing
RFLP (Restriction fragment length polymorphism)

Question 26

Give advantages of using typing methods for ID of a pathogen (x5)

Answer 26

Increased sensitivity and specificity of diagnosis
Faster
Good for organisms that are hard to culture
Identification of carriers
Outbreaks can be detected earlier on

Question 27

What is meant by disease ecology

Answer 27

Looking at how the disease affects the host, and how it is transmitted

Question 28

What does disease ecology require

Answer 28

Knowledge of the pathogen
E.g. transmission routes, optimal environments, what ‘states’ animals in the population are in

Question 29

Name the 4 possible ‘states’ an animal can be in with regard to susceptibility to disease

Answer 29

Susceptible - not got disease
Infected - have the disease
Recovered - have had the disease
Potentially susceptible again - can be reinfected

Question 30

Name the 3 main factors in combatting disease

Answer 30

Disease prevention
Disease control
Disease eradication

Question 31

What are the 3 groups that can be targeted in disease prevention and control and how

Answer 31

Host - increasing resistance/decreasing susceptibility
Environment - decrease pathogen transmission
Pathogen - decrease pathogen population

Question 32

List 5 methods of reducing pathogen transmission in the environment

Answer 32

Restriction of host movement
Quarantining/isolation
Control of vectors
Biosecurity
ID those that need to be restricted

Question 33

Name the 4 approaches to disease eradication and describe them

Answer 33

Test and removal - animals that test +ve are removed and slaughtered
Pre-emptive - Animals that have been exposed are slaughtered
Blanket culling - animals on contagious premised surrounding an infected farm are culled
Stamping out - combination of one of the methods above with other preventative methods

Question 34

What additional factors should be considered when approaching disease control (x3, 1 extra)

Answer 34

Economics
Socioeconomics
Welfare
(mental health??)

Question 35

Name the 4 post common food borne pathogens

Answer 35

Campylobacter
Clostridium perfringens
Norovirus
Salmonella

Question 36

What does DALY stand for

Answer 36

Disability-adjusted life year