1
Q
Purpose of Analytical Studies?
(2)
A
- ID & explain the cause of dz
- numerically assess risk factors
2
Q
3 parts of an Analytical Study?
A
- Data collection
- Data analysis
- Data interpretation
3
Q
Study type that compares dz occurrence between “exposed” & “non-exposed”
A
Cohort study
4
Q
2 Strengths of Cohort Studies
A
- Rare exposure
- can examine multiple outcomes of a single exposure
5
Q
Weaknesses of Cohort Study
(2)
A
- Not good for rare dz.
- time consuming if there is a long period between exposure & dz.
6
Q
Prospective Cohort follows groups from _______ to ________.
A
present to future
7
Q
Strengths of Prospective Cohorts
(3)
A
- measure Incidence
- describes temporal relationships
- collect data on possible confounders
8
Q
Weaknesses of Prospective Cohorts?
(3)
A
- Expensive & long
- Lack of follow-up can affect validity
- Requires a large # of subjects
9
Q
Retrospective Cohort follows subjects from _______ to _______.
A
present to past
10
Q
Strengths of Retrospective Cohorts
(3)
A
- data is already present
- cheap
- easy to perform
11
Q
Weaknesses of Retrospective Cohorts
(2)
A
- Need good records → confounders
- Selection bias
12
Q
Relative Risk looks at what?
A
how many times more/less likely exposed individuals are to get the dz. relative to non-exposed individuals
13
Q
How do you calculate RR?
A
14
Q
Purpose of Cofidence Interval (CI)?
A
allows you to determine whether or not the RR/OR can be deemed statistically significant
15
Q
When is the result said to be statistically significant?
(in regards to the CI)
A
- if the CI falls entirely on either side of the null value (1.0)
- has be 95% or higher
16
Q
_______ are study subjects who have the disease of interest in Case-Control Studies.
A
Cases
17
Q
What is the purpose of Case-Control Studies?
A
compare frequency of exposure factors in cases w/ dz and cases w/o dz.
18
Q
_______ are subjects who are dz free at the time of selection in Case-Control Studies.
A
Controls
19
Q
Where does Case Selection come from?
A
- all cases in a defined population or from the general population
- often more convient
20
Q
Controls selected from CCS should be __________ to cases in every respect except _______.
A
- identical
- disease
21
Q
How do you calculate Odds Ratio (OR)?
A
22
Q
Which study uses OR?
A
Case-Control Studies
23
Q
4 Strengths of Case-Control Study?
A
- Rare dz.
- Multiple exposure
- cheap & fast
- Small # of subjects
24
Q
4 Weaknesses of Case-Control Studies?
A
- No Incidence or Prevalence
- Bias→ recall, selection, information, misclassification
- Difficult to establish temporal relationships
- Cofounding
25
Objective of Randomized Clinical Trials (RCTs)?
subjects followed over time to test possible effects of therapeutic & preventative interventions
26
Which RCT evaluates whether agent/procedure reduces risk of dz. developing in those currently free from dz?
Field Trial
| (Prevention Trial)
27
3 Strengths of RCTs?
* Control over study situation
* Casual relatioship can be established
* Reduced confounding & bias
28
5 Weaknesses of RCTs?
* May not accurately represent normal population
* Need large sample size → $$
* May be timely
* Ethical issues
* Bias if no blinding is present
29
Test that is:
* Applied to animals showing CS of dz.
* Confirms or classifies dz. status
DX tests
30
This test is used to:
* to ID undiagnosed cases of dz in apparently healthy populations
Screening tests
31
Sensitivity means?
Probability that a disesed patient will test positive
32
Specificity means?
Probability that a healthy patient will test negative
33
What must you use to calculate Sensitivity & Specificity?
Gold Standard Tests
34
True Positive (**TP**) means?
a diseased patients that test positive for dz.
35
True negative (**TN)** means?
healthy patient that tests negative for dz
36
False Positive (**FP**)?
Healthy patient tests POSITIVE
37
False Negative (**FN**)?
Sick patient tests NEGATIVE
38
Calculate **Sensitivity**!
_TP_
Dz (+)
39
Calculate **Specificity**!
_TN_
Dz. (-)
40
Calculate **Prevalence**!
_ Dz (+) _
Total tested
OR
_ (a+c) _
(a+b+c+d)
41
Calculate **Positive Predictive Value (PPV)**!
## Footnote
*# of diseased subjects that test (+) for dz of interest*
42
Calculate **Negative Predictive Value (NPV)**!
## Footnote
*Healthy subjects that test (-) for dz of interest*
43
When is it feasible to implement a Screening Program?
(5)
* Dz. is important to public health
* Test will have a high level of case detection & low level of FPs
* Have facilities available for follow-up & TX
* Test doesn't harm patient
* cost effective
44
List the 6 steps of Natural HX of Dz in order!
* biological onset
* preclinical phase
* detectable preclinical phase
* lead time
* critical points
* clincal phase
45
Phase of Natural HX of DZ where there are no symptoms & may only have sub-cellular changes in DNA?
Biological onset
46
Phase of Natural HX from biological onset to developement of CS of dz?
Preclinical Phase
47
The point during preclinical phase before symptoms develop, but dz can be detected using screening tests?
Detectable preclincal phase
48
Interval by which time of DX is advanced by early screening & early detection methods?
Lead Time
49
Point(s) in natural HX BEFORE which TX in effective?
Critical Points
50
List order of the **Chain of Infection**!
agent → reservoir/host → portal of exit → transmission → portal of entry → susceptible host
51
T/F: All Amplifier Host = Essesential Hosts
FALSE
52
T/F: All Essential Hosts= Amplifier Hosts
TRUE!!!
53
Key Requirement for INFECTION!
host shows IMMUNE RESPONSE
54
Time period btwn exposure to an agent & onset of CS of dz?
Incubation period
55
The interval between exposure to an infectious organism and the clinical appearance of disease
Latent Period
56
Clinically apparent infection = ?
DISEASE
57
4 possible outcomes of Infection?
* Immunity
* DZ
* Subclincal Infection
* Carrier state
58
**Antigenic Drift** is responsible for what 2 things?
* **small, gradual mutations**
* account for **annual epidemics**
59
**Antigenic Shift** is responsible for what things?
* **abrupt, major changes**
* **new disease states** (ex. H1N1)
60
Calculate **Infectivity**!
_ infected animals _
exposed animals
61
Calculate **Attack Rate**!
## Footnote
*(infectivity during an outbreak)*
_# new cases per period_
entire population
62
Calculate **Secondary Attack Rate**!
## Footnote
*(susceptible animals following known contact w/ 1° case)*
_ # of new cases from 1° case _
all those healthy after contact w/ 1° case
63
Calculate **Pathogenicity**!
## Footnote
*(proportion of infected animals that develop CS)*
_ # of infected w/ C.S. _
All infected individuals
64
Calculate **Virulence**!
## Footnote
*(# of animals that develop severe dz)*
_ # w/ severe dz _
All dz. animals
65
Calculate **Case-Fatality Rate**!
## Footnote
*(proportion of cases that evenutally die from dz)*
_ # fatal cases _
All dz animals
66
Calculate **Mortality Rate**!
## Footnote
*(reflects burden of deaths from dz in the population as a whole)*
_ # of deaths from dz _
Total population
67
What season are respiratory diseases more prevalent?
Winter
68
What season are food-borne & vector-borne diseases more prevalent?
Summer
69
**CDC** definition of **Herd Immunity**?
accomplished when # of animals w/ acquired immunity is so great that, under natural conditions, a infectious agent can't enter into or spread w/in a herd.
70
What happens to Herd Immunity when you introduce **susceptible animals** to a herd?
(2)
* host resistance is reduced
* Increase in occurrence of infection & dz.
71
What happens during the **Descriptive Phase** of an **Outbreak Investigation**?
1. describe dz parameters
2. take herd HX
3. form case definition
4. make epidemic curve
72
List the 3 components of Case Criteria.
1. CS
2. immunologic response
3. ability to detect agent & confirm it as the cause
73
List the 4 Phases of Outbreak Investigation.
1. Descriptive
2. Analytical
3. Invervention
4. Control
74
Which 2 biological disasters are FAR more likely to occur?
Natural disasters
Accidental disasters
75
List the 3 consequences of all Biological Disasters
Health/Economic impact
Psychological impact
Improved Preparedness
76
**Agroterrism** definition?
intent to indirectly attack persons by destruction of plant & animal infastructure of a nation
77
**CDC Bioterrorism** definition?
deliberate release of viruses, bacT or other agents used to cause illness/death in people, animals or plants
78
4 Clues to Occurence of Agro/Bioterrorism
* Clustering of dz (normally healthy populations
* Dz outside normal/expected season
* Dissemination over very large areas quickly → if airborne
* Acute morbidity/mortality
79
_These agents belong to what CDC Category?_
## Footnote
Ebola
* Y. pestis* (plague)
* B. anthracis* (anthrax)
* C. botulinum* (botulism)
* V. major (*small pox)
* F. tularensis* (tularemia)
* Lassa* virus
Category A
## Footnote
*highest priority*
80
What 3 requirements must an agent meet to be considered **CDC Category A agent**?
* easily transmitted from person to person
* High mortality rate
* requires special action for public health preparedness
81
What 3 requirements must an agent have to be considered a **CDC Category B agent**?
* moderately easy to disseminate
* Moderate morbidity & low mortality rates
* requires enchanced DX capacity & DZ surveillance
82
_These agents are all classified under what CDC Category?_
## Footnote
* Brucella*
* C. burnetti* (Q fever)
* Salmonella, E. coli, Shigella*
* B. mallei (*Glander's)
* B. pseudomallei (*Melioidosis)
* C. psittaci* (Psittacosis)
* R. prowazekii* (epidemic typhus fever)
* Alphaviridea* (EEE, WEE, VEE)
* Crytosporidium*
* V. cholerae*
**Category B Agents**
*second highest priority*
83
What 3 requirements are needed to be considered a **CDC Category C agent**?
* emerging pathogens→ ability to be engineered for mass dissemination
* easy to produce & spread
* potential for high morbidity/mortality rates → major health probs.
84
List the 2 **CDC Category C agents**!
Nipah virus
Hanta virus
85
List the 5 agents in **Tier 1 of the Select Agent Program**!
## Footnote
*HHS & APHIS of USDA*
1. **FMD→ highest priority**
2. Classical Swine Fever
3. Newcastle Dz.
4. Vesicular stomatitis
5. Avian influenza → highly pathogenic form
86
What is the lead federal agency in safeguarding America's livestock & poultry health?
APHIS of the USDA
