Definitions

Question 1

Epidemiology

Answer 1

The study of the frequency, distribution, and determinants of health and disease in populations, and the application of this study to the control of diseases.

Question 2

Health

Answer 2

A state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.

Question 3

Disease

Answer 3

A physiological/psychological dysfunction.

Question 4

Epidemiologist

Answer 4

One who understands the principles of epidemiologic research and has the experience to apply them. It is not necessary to be a physican, veterinarian or statistician.

Question 5

Illness

Answer 5

A subjective state of the person who feels aware of not being well.

Question 6

Disease sign

Answer 6

Something you can see or measure i.e. fever

Question 7

Disease symptom

Answer 7

Self-reported, cannot see or measure i.e. aches

Question 8

Disease syndrome

Answer 8

A combination of signs and symptoms that may indicate a certain disease.

Question 9

Bias

Answer 9

Any systematic error in the design, conduct and analysis of a study that results in a mistaken estimate of an exposure’s effect on the risk of disease (or the outcome).

Question 10

Systematic

Answer 10

Done according to a fixed plan, methodical.

Question 11

Validity

Answer 11

The absence of systematic bias in results.

Question 12

Internal validity

Answer 12

The ability to make unbiased inferences about the association of interest in the study population. “The ability to get the right answer.”

Question 13

External validity

Answer 13

The ability to make unbiased inferences about the association of interest to populations beyond the source population.

Question 14

Confounding bias

Answer 14

Occurs when the observed association between the exposure and outcome is mixed up with a third factor. Occurs when a true counterfactual state is not achieved.

Question 15

Epidemiologic triad

Answer 15

Interaction between host, agent and environment to cause disease

Question 16

Primary or definitive host

Answer 16

A host in which the agent reaches maturity and, if possible, reproduces sexually

Question 17

Dead-end or incidental host

Answer 17

A host in which the agent is not able to transfer to the definitive or primary host, preventing the agent from completing its lifecycle. An type of intermediate host.

Question 18

Amplifying host

Answer 18

A host in which the level of the agent can become high enough that a vector that feeds on it will probably become infectious.

Question 19

Secondary or intermediate host

Answer 19

A host that harbours the agent for a short transition period, during which some developmental stage may be completed.

Question 20

Primary prevention

Answer 20

Prevent exposure to the the causal factor

Question 21

Secondary prevention

Answer 21

Detect disease before clinical disease occurs.

Question 22

Teritary prevention

Answer 22

Diagnose and treat clinical disease

Question 23

Incidence

Answer 23

The number of new cases in a defined population during a specific time period

Question 24

Prevalence

Answer 24

The number of cases in a defined population at a point in time, or period of time.

Question 25

Horizontal transmission

Answer 25

Transmission from one host to another, either directly or indirectly through an intermediate host or vector

Question 26

Vertical transmission

Answer 26

Transmission from mother to child, in utero, in ovo, and via milk

Question 27

Infectivity

Answer 27

How many organisms are required to cause disease

Question 28

Virulence

Answer 28

The ability of an organism to cause disease or damage to the host

Question 29

Communicability

Answer 29

The time in which the disease can transfer from one individual to another.

Question 30

Reservoir

Answer 30

Any person, animal, arthropod, plant, soil or substance (or combination of these) in which an infectious agent normally lives and multiplies, on which it depends primarily for survival, and where it reproduces itself in such manner that it can be transmitted to a susceptible host

Question 31

Carrier

Answer 31

A person or animal that harbors a specific infectious agent without discernible clinical disease and serves as a potential source of infection. May be short or long duration.

Question 32

Incubation period

Answer 32

Time from exposure to start of clinical disease.

Question 33

Latent period

Answer 33

Time from exposure to pathological changes in the host.

Question 34

Sensitivity

Answer 34

The proportion of diseased individuals that test positive. The probability of detecting a disease positive individual with the test. The proportion of true positives that are correctly identified by the test.

Question 35

Specificity

Answer 35

The proportion of disease negative individuals that test negative. The probability of detecting a disease negative individual with the test. The proportion of true negatives that are correctly identified by the test.

Question 36

False positive fraction

Answer 36

The proportion of disease negative individuals that test positive.

Question 37

False negative fraction

Answer 37

The proportion of disease positive individuals that test negative.

Question 38

Positive predictive value

Answer 38

The proportion of test positive individuals that are truly diseased. A measure of how useful a test is when applied to individuals with unknown disease status.

Question 39

Negative predictive value

Answer 39

The proportion of test negative individuals that are truly disease free. A measure of how useful a test is when applied to individuals with unknown disease status.