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1
Q

Surveillance. Think what 2 things?

A

Surveillance​

Prevalence

Incidence rate

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2
Q

Prevalence is a _ of a population at a given point in time

Incidence is a _ of a population at a given point in time

A

Prevalence is a measure of the state of a population at a given point in time

Incidence is a measure of events of a population at a given point in time

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3
Q

Cumulative incidence is the _ of new cases that develop in a population _

equation?

A

Cumulative incidence is the proportion (risk) of new cases that develop in a population over time

CI = Pr(New Disease) = risk of disease =​ (# new cases)/ pop at risk….. over time t

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4
Q

Incidence rate is the instantaneous or _

It is not a _ or _

equation?

A

Incidence rate is the instantaneous or average rate of disease occurrence

It is not a probability or proportion

IR=Rate of disease= (# cases)/(Persons at risk * time) or (sum of person time from follow up)

  • person time
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5
Q

RR equation

A

RR= P(D+, E+)/ P(D+/E-).. over time t

RR= CI exposed/ CI unexposed.. over time t

CI exposed= (cases w/ exposure)/(person w/ exposure at risk)

CI unexposed=(cases w/o exposure)/(persons w/o exposure at risk)

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6
Q

Risk difference eqt

A

I1-I0

Incidence among exposed- incidence among unexposed

the exposure is associated with a _% absolute increase in risk, compared to the unexposed group

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7
Q

Incidence rate ratio eqt

A

IRR= (rate of disease in exposed)/(rate of disease in unexposed)

IRR= (incidence rate in exposed)/(incidence rate unexposed)

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8
Q

Odds ratio or exposure OR

A

[(E+,D+)/(E-,D+)]/[(E+,D-)/(E-,D-)

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9
Q

Components of an Outbreak Investigation

1) Verify the _ and confirm the _
2) Define a _ and conduct _ _
3) Tabulate and orient _: _, _, and _
4) Take immediate _ _
5) Formulate and test _
6) Plan and execute _ _
7) Implement and evaluate _ _
8) Communicate _

A

Components of an Outbreak Investigation

1) Verify the diagnosis and confirm the outbreak
2) Define a case and conduct case finding
3) Tabulate and orient data: time, place, and person
4) Take immediate control measures
5) Formulate and test hypothesis
6) Plan and execute additional studies
7) Implement and evaluate control measures
8) Communicate findings

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10
Q

Steps to determine if an outbreak is real

1) verify _
2) define a _
3) ID & count _
4) _ vs _
5) rule out other _

A

Steps to determine if an outbreak is real

1) verify diagnosis
2) define a case
3) ID & count cases
4) Observed vs expected
5) rule out other reasons

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11
Q

Hypothesis generating vs. hypothesis testing

A

Hypothesis generating:

  • Attempt to identify most likely exposures

- Cases only, limited number

- Open-ended questions

Hypothesis testing:

  • Focus on most likely cause or causes
  • Include comparison group
  • Closed-ended question
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12
Q

Attack rate= _

Eqt?

A

Attack rate= CI

(New cases)/(Population at risk)…. over time t

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13
Q

Secondary attack rate

Secondary Attack Rate = P(D+|_)

Secondary Attack Rate = P(D+|_)

A

Secondary attack rate

Secondary Attack Rate = P(D+|Contact with a known case)

Secondary Attack Rate = P(D+|Exposure to a known case)

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14
Q

Describe common source point epidemic

A

Sharp slope w/ gradual downslope

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15
Q

Describe Common Source Point with Secondary Transmission (Mixed)

A

Initial point source with subsequent person-to-person transmission

May have either:
a bimodal appearance Or
a prolonged downslope

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16
Q

Describe Common Source Continuous Epidemic

A

Rise sharply, as with point source

Plateau reached and sustained

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17
Q

Describe a propagative epidemic

A

Encompasses several generations of the agent

Begins with single case or small number of cases

Downslope related to exhaustion of susceptible hosts

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18
Q

What outbreak?

A

Common Source Continuous

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19
Q

What outbreak?

A

Common Source Point

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20
Q

What outbreak?

A

Propagative

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21
Q

What outbreak?

A

Common Source Intermittent

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22
Q

Simple Structure of Four Study Designs

A

A) Pros Cohort

B) Retro Cohort

C) Case Control

D) Cross-sectional

23
Q

Best use for cohort study (2)

A

short latent period

well-defined pop at risk

24
Q

Best uses for case-control

A

Long latent period

unclear pop at risk

common exposure

25
Q

best use cross-sectional

A

initial evaluation- Used to take out population that isnt at risk anymore

26
Q

Study design: Cross Sectional

Measure of frequency:

Measure of association:

A

Study design: Cross Sectional

Measure of frequency: Prevalence

Measure of association: Prevalance ratio

27
Q

Study design: Case Control

Measure of frequency

Measure of association

A

Study design: Case Control

Measure of frequency: None

Measure of association: Odds ratio

28
Q

Study design: Retrospective cohort

Measure of frequency: Cumulative incidence

Measure of association

other consideration

A

Study design: Retrospective cohort

Measure of frequency: Cumulative incidence

Measure of association: Risk ratio

other consideration: Use with minimal loss to follow-up

29
Q

Study design: Retrospective cohort

Measure of frequency: Incidence rate

Measure of association

other consideration

A

Study design: Retrospective cohort

Measure of frequency: Incidence rate

Measure of association: Incidence rate ratio

other consideration: Use with loss to follow-up; recurrent disease

30
Q

Study design: Prospective cohort

Measure of frequency: Cumulative incidence

Measure of association:

other consideration

A

Study design: Prospective cohort

Measure of frequency: Cumulative incidence

Measure of association: Risk ratio

other consideration: Use with minimal loss to follow-up

31
Q

Study design: Prospective cohort

Measure of frequency: Incidence rate

Measure of association

other consideration

A

Study design: Prospective cohort

Measure of frequency: Incidence rate

Measure of association: Incidence rate ratio

other consideration: Use with loss to follow-up; recurrent disease

32
Q

Epi causal triad

A

Host

Agent

Environment

33
Q

Epi causal triad: AGENT (3)

A

Infectivity; pathogenesis; virulence;

34
Q

Infectivity

The characteristic of the agent that reflects the ability to _, _, and_.

A

Infectivity

The characteristic of the agent that reflects the ability to enter, survive, and multiply in the host.

35
Q

Pathogenicity

Property of an organism that determines the _ to which overt disease is _ in _

A

Pathogenicity

Property of an organism that determines the extent to which overt disease is produced in an infected population

36
Q

Virulence:

A measure of the _ caused by an organism

A

Virulence:

A measure of the severity of the disease caused by an organism

37
Q

Infectivity eqt

A

people infected/ people exposed

38
Q

pathogenicity eqt

A

clinical cases/ people infected

39
Q

virulence eqts

A

severe cases/ clinical cases

severe cases/ people infected

clinical cases/ people infected

40
Q

incubation period

A

time between infection and clinical symptoms

41
Q

Latent period

A

time between infection and infectious period

42
Q

serial interval

A

time between clinical symptoms in 1* and 2*

43
Q

what comes first, infectious period or clinical symptoms?

A

infectious period

44
Q

Reproductive (reproduction) number (R)

average number of _ per I

A

Reproductive (reproduction) number (R)

average number of successful transmissions per infectious person

Secondary cases/ primary cases

45
Q

R: When will an epidemic stop?

A

So with R < 1, the epidemic is not sustainable

46
Q

When should R be at a maximum?

R0: Basic reproductive number

A

If everyone is susceptible (s = 1), R should be at its maximum.

R0 = average number of secondary cases caused by a single, typical person in a completely susceptible population

47
Q

Rn : Net (effective) reproductive number

If the infection is initiated in a population with <100% susceptibility, the net R (Rn) will be less than _

Similarly, as the number of susceptible persons in a population is not stable (e.g. disease causes immunity), _

A

Rn : Net (effective) reproductive number

If the infection is initiated in a population with <100% susceptibility, the net R (Rn) will be less than R0

Similarly, as the number of susceptible persons in a population is not stable (e.g. disease causes immunity), R will change over time​

48
Q

Rn: Function of R0 and proportion susceptible

eqt?

A

Rn =R0*s
Where s = proportion of the population that is susceptible to the infection

49
Q

Herd immunity threshold (HIT) eqt

If the population can attain a level of immunization (or immunity) > HIT, what will happen?

A

HIT= 1–s =1–1/R0

HIT=(R0 –1)/R0

If the population can attain a level of immunization (or immunity) > HIT, what will happen? The epidemic should end

50
Q

Components of R0

A

R0 = pcD

transmission probability (p);

contact rates (c);
length of infectious period (D);
51
Q

Rn = R0_= pcD_

A

Rn = R0s = pcDs

transmission probability (p);

contact rates (c);
length of infectious period (D);

proportion of susceptibles (s)

52
Q

What does the relationship R = pcDs suggest about potential targets / mechanisms for control strategies?

A

Reduce transmission probability (p); early treatment
Decrease contact rates (c); stay home!!! (quarantine)
Reduce length of infectious period (D); treatment
Reduce proportion of susceptibles (s): flu shots (immunization)

53
Q

Cancer Clusters difficulties

A

Clusters sometimes result from confounders

Difficult to establish a cause-and-effect relationship between disease and exposure

extra

Often fail to come to a satisfactory conclusion.

Unable to confirm a geographical or temporal excess in the number of cases

A cluster may be a collection of several diseases

Establishing source of cluster very difficult

54
Q

Cancer cluster Preliminary Evaluation: SIR

A

Standardized incidence ratio

Number of observed/ expected

Non-infectious disease

Outbreak Final (5 decks)

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