Classes #3-#7: Descriptive Epidemiology and Measures of Disease Frequency Flashcards
What are the 3 different surveillance systems used by epidemiologist?
- Passive Surveillance System
- Active Surveillance System
- Syndromic Surveillance System
- Dr. Segars also discussed Biosurveillance (human, plant, animal, and environment)
What is a passive surveillance system?
Relies on a healthcare system to follow regulations on required reportable diseases/conditions (e.g: a doctor reporting a disease in his patients).
*public health system passively waits for reports to come in, in order to track disease frequency/occurrence over time and within populations.
Describe what an active surveillance system is.
public health officials go out into the community to search for new disease/condition cases.
Define what a syndromic surveillance system is.
A system that looks for pre-defined signs/symptoms of patients, either being reported or evaluated.
What do you think is the most critical element that must be defined before any of the W’s of descriptive epidemiology can be accomplished?
“Case” Definition – The definition of disease. The epidemiologist has to know what they’re looking for.
This is called Diagnostic Criteria – In medicine this is called set criteria.
What is a “case” definition?
Is a set of uniform criteria used to define a disease/condition for public health surveillance.
>enable public health to classify and count cases consistently across reporting jurisdictions
>while the list of reportable conditions varies by state, the CSTE has recommended that state health departments report cases of selected diseases to NNDSS
>every year, case definitions are updated using CSTE’s Position Statements. They provide uniform criteria of nationally notifiable infectious and non-infectious conditions for reporting purposes.
>Epidemiologists and Healthcare providers must carefully and consistently define and execute exactly HOW we will detect (diagnose) what we want to, or have to, count; accurately! (Confirmed vs. Probable case definitions)
(The reported Criteria changes with knowledge of the disease, which is handle and carried out by the CSTE)
What is the definition of epidemic?
The occurrence of disease clearly in excess of normal expectancy.
>community/period clearly defined
>goal is to capture disease as early as possible
What is the definition of outbreak (cluster)?
An epidemic limited to a localized increase in the occurrence of disease. (sometimes interchanged with “cluster”)
What is the definition of endemic?
The constant presence of a disease within a given area or population in excess of normal levels in other areas. (e.g: HIV in Africa is an Endemic)
What is a Pandemic?
An epidemic occurring over a very wide area involving a large number of people.
>many times multi-region or multi-national
>when disease crosses country to country
What is “The Epidemic Curve”?
A visual depiction created during an outbreak/epidemic of the # of cases; by date of onset.
> Visually Depicts
What tool do epidemiologist construct/use to help form hypotheses on routes of transmission, probable exposure period, and incubation period (may help identify/eliminate causes)?
An Epidemic Curve
What type of epidemiology is used to determine if a site/location is experiencing disease occurrence MORE FREQUENTLY THAN USUAL (for the location)?
Descriptive Epidemiology
What are the 3 basic types of relative measures of disease frequencies utilized by epidemiologists (either within a group or between groups)?
1) Ratios
2) Proportions
3) Rates
How do you calculate a ratio, and what does it tell you?
A ratio is the division of 2 unrelated numbers.
>the numerator is not part of the denominator
> e.g: YES / NO
