midterm

Question 1

epidemiologic triad

Answer 1

host, agent, environment, vector

Question 2

endemic

Answer 2

usual disease occurrence in a geographic area

Question 3

outbreak

Answer 3

unexpected increase in endemic disease cases

Question 4

epidemic

Answer 4

in excess of normal disease cases

Question 5

passive surveillance

Answer 5

often voluntary reporting, “chance favors the prepared mind”

Question 6

active surveillance

Answer 6

mandatory or regular reporting in a defined population

Question 7

direct transmission

Answer 7

person-to-person, e.g. sneezing, aerosolized, fluid

Question 8

indirect transmission

Answer 8

transmission through intermediates, e.g. common vehicle (water for cholera), vector (mosquitos for yellow fever), or zoonotic reservoir (pets and lyme)

Question 9

types of diffusion

Answer 9

expansion/contact and relocation

Question 10

types of disease cases

Answer 10

index (first to be identified), primary (brings infection to a population), secondary (infected by a primary case), tertiary (infected by a secondary case)

Question 11

epidemic curve components

Answer 11

infusion (small proportion infected), inflection (rapid increase in infecteds), saturation (decrease in susceptibles), waning (decrease in infecteds)

Question 12

epidemic curve types

Answer 12

one incubation period (single peak), multiple incubation periods (consistent levels over time), multiple waves (multiple peaks)

Question 13

contagiousness/attack rate definition

Answer 13

likelihood that infection will be transmitted

Question 14

attack rate formula

Answer 14

of people at risk who develop disease / # of total people at risk

Question 15

case fatality rate definition

Answer 15

likelihood of dying once you have the disease

Question 16

case fatality rate formula

Answer 16

(# of deaths from a disease / # of diagnosed cases of that disease) * 100

Question 17

reproductive rate

Answer 17

average number of people infected by one infectious individual (R0)
R0 < 1 = the infection will eventually disappear
R0 > 1 = the infection will be able to spread in the population

Question 18

dispersion factor

Answer 18

small number of highly infectious people disproportionately impact the number of secondary cases (K)

Question 19

incubation period

Answer 19

time period between exposure and onset of disease symptoms

Question 20

communicable period

Answer 20

time during which a pathogenic agent may be transmitted

Question 21

SEIR model

Answer 21

susceptible (yet to be infected)
exposed (latent infected, not yet transmitting –> dead ends never become infectious)
infectious (actively able to transmit; carriers)
recovered (immune/can no longer develop disease)

Question 22

herd immunity

Answer 22

increase the immune population, reduces rate by interrupting chain of transmission. you do NOT need to immunize 100% of the population

Question 23

prevalence (formula)

Answer 23

(# of cases of a disease present in a population at a specified time / # of persons in the population at that specified time) * 100

Question 24

cumulative incidence formula

Answer 24

of new cases / # of persons at risk at beginning time period

Question 25

incidence rate formula

Answer 25

IR
of new cases during the time period / total person-time of observation

Question 26

relative risk or rate/risk ratio formula

Answer 26

RR
incidence of disease in the exposed / incidence of disease in the unexposed
(a / a+b) / (c / c+d)

Question 27

attributable risk formula

Answer 27

AR
incidence of disease in the exposed - incidence of disease in the unexposed
(a / a+b) - (c / c+d)

Question 28

attributable risk percent formula

Answer 28

AR%
(AR / incidence of disease in the exposed) * 100
(Ie - Io) / Ie *100

Question 29

population attributable risk formula

Answer 29

PAR
incidence in total - incidence among unexposed

Question 30

population attributable risk formula

Answer 30

PAR%
(PAR / incidence in total) * 100

Question 31

cause definition

Answer 31

X causes disease for an individual if and only if the individual has X and gets the disease, and at the same moment in time with all else equal, the same individual would not have gotten the disease without X

Question 32

mackie’s counterfactual definition of cause

Answer 32

X and Y occurred and, within a causal field, in the circumstances, Y would not have occurred if X had not at least when and how it did

Question 33

rothman’s definition of a cause

Answer 33

a cause of a disease is an event, condition, or characteristic that preceded the disease event and without which the disease event would not have occurred at all or would not have occurred until some later time

Question 34

risks that result in association and not causation

Answer 34

reverse causation, noncomparabilty/confounding, study artifacts (chance, selection bias, misclassification)

Question 35

necessary cause

Answer 35

cannot get disease without it. in the pie model, it is present in all pies

Question 36

sufficient cause

Answer 36

when all components are present, disease will occur. in the pie model, the entire pie is required

Question 37

INUS causes

Answer 37

insufficient but
necessary component of
unnecessary but
sufficient cause

Question 38

randomized controlled trial features

Answer 38

RCT
- a prospective study in humans using randomization to compare the effect of an intervention against a control
- random assignments of exposure/nonexposure in a group of individuals that are otherwise the same

Question 39

as-treated definition

Answer 39

evaluating data based on which group each participant fell in based on participant behavior (ie if a participant failed to keep up with exposure, assign them to nonexposure). not recommended to do because it eliminates comparability by introducing selection bias

Question 40

intent-to-treat definition

Answer 40

evaluating data based on which group each participant was assigned to, regardless of whether they followed through. recommended because it maintains comparability between groups