Reporting Disease Occurence Flashcards
What 3 things make up the Epidemiologic Triangle?
- Host
- Environment
- Agent
What does the Epidemiologic Triangle represent?
- Traditional model of causation for dz.
- whether or not a dz will occur in an individual
What 3 things determine the level of DZ in a population?
- Individual factors
- Spatial factors
- Temporal factors
(who, when, where!)
How may we report the occurence of a DZ & it’s frequency? (4)
- Onset in time
- By time series analysis
- Host related factors
- Geographical location
- Combo of above
Temporal Dimensions of Dz focus on what?
Whether or not a DZ is endemic, sporadic, epidemic or pandemic
How does an Endemic DZ occur?
(3)
- occurs at expected frequency
- present at all times
- usually low & predictable levels
How does an Epidemic Dz occur?
(2)
- occurs at greater than expected frequency
- can be depicted graphically as epidemic curves
When does a Sporadic DZ occur?
(3)
- single case or small cluster of cases
- infrequently
- irregular & unpredicatable
List the 3 basic Epidemic Curves.
- Point Source Epidemic
- Continous, Common Source Epidemic
- Propagating Epidemic
What type of Epidemic Curve is this?
Point Source
List the characteristics of a
Point Source Epidemic Curve
- Population is subjected to the same BRIEF exposure over a defined period of time (usually 1 intubation period)
- Shape: rises rapidly, definite peak, followed by a decline
- No new cases occur once the point source is removed
What type of Epidemic curve is this?
Continous, Common Source Epidemic
List the characteristics of a
Continous, Common Source Epidemic.
- Prolonged exposure to the source over an extended period of time ( >1 intubation time)
- Sharp down slope= common source removed
- Gradual down slope= outbreak exhausts itself
What type of Epidemic curve is this?
Propagating Epidemic
______ epidemic occurs when a DZ is introduced through a single source and subsequently transmitted to others (2O cases)
Propagating Epidemic
What form of analysis uses information of patterns of DZ occurence obtained form temporal occurence?
Time Series Analysis
Purpose of Time Series Anaylsis?
ID persons of high or low risk so causal assocations can be explored
3 trends that influence patterns of DZ occurence?
- Short-term
- Cyclical (+ seasonal)
- Secular (long term)
Trend Characteristics:
- Rise & fall of a DZ over > 1 yr.
- Regular, periodic fluctations in level of DZ occurence
Cyclical trends
Trend Characteristics:
- Special case of cyclical trend
- periodic fluctuations in DZ incidence related to particular seasons
Seasonal Trends
4 things that cause fluctuations in
Seasonal Trends?
- host density
- management practices
- vectors
- infectious agent survival
Overall rise or decline in incidence occuring gradually over long periods of time
Secular Trend
- Describes the proportion of a population, initially free of the DZ of interest, that develops the DZ over a given period of time.
- Refers to NEW cases of dz.
Incidence
How do you calculate Incidence?
Per # of individuals
(unit of population expressed as whole #s & in smallest multiples of 10)
- Proportion of the population at a given time that have the factor of interest.
- Expressed either as a proportion btwn 0-1, as a %, or as a # per unit of population at risk
Prevalence
How do you calculate Prevalence?
Which measure takes into account the duration of disease?
Incidence
An important measure of the burden of DZ in the population & is useful in developing health policies
Prevalence
What is the relationship between
Incidence & Prevalence?
Prevalence (P) = Incidence (I) x Duration of DZ (D)
P = I x D
What can cause a change in Prevalence?
(3)
Changes in:
- Incidence
- Avg. Duration of DZ
- Both Indicence & Duration of DZ
Importance of Prevalence?
- Existing cases of DZ
- Indentify major DZ problems
- Identify/evaluate control strategies
2 Reasons to use Incidence?
- predict population’s health status
- Assess the probablility that an animal w/in a population at risk may develop the DZ of interest
Purpose of Data Visualization (mapping)
& Data description?
Show the location of diseased animals w/in a defined geographical limit
Purpose of Data modeling?
Test hypotheses & plan health policies
Why is Cluster Analysis important?
- Classifies dz basedon time:location clustering to exipidite prevention/control
- Determine whether or not the dz warrants concern (epidemic)
Purpose of an Epidemic Curve?
main way to identify the source of a dz.
Key characteristics of a Sporadic Dz?
- small # of cases
- occurs rarely & w/o regularity
- no secondary cases
Incidence is usually expressed numerically in reference to what?
Population at risk
How is prevalence expressed?
(3)
- proportion btwn 0 & 1
- a %
- a unit of population at risk
Prevalence does not take into account what?
Duration of the dz.
