Descriptive Epidemiology & Measuring Disease Frequency Flashcards
The membership of this type of population is PERMANENT and defined by an event (ex: victims of 9/11, or women age 65+)
Fixed population
The membership of this type of population is TRANSIENT and defined by being in or out of a particular “state” (ex: residents of the city of Honolulu or employed at Starbucks)
Dynamic population
These statistics are useful for:
- Understanding the health status of a population
- Formulating hypothesis about etiology or the cause of disease, and
- Planning, implementing, and evaluating public health programs to control and prevent adverse health events
Descriptive Epidemiological Statistics
Name the first 4 W’s (out of 5 W’s) of Descriptive Epidemiology
- What
- When
- Where
- Who
Measures of risk/disease frequency should take into account these 3 KEY ASPECTS:
- Number of individuals affected w/the disease
- Size of source population (total at risk for disease or exposed)
- Length of time the population was followed
A set of uniform criteria used to define a disease for public health surveillance. Enables public health to classify and count cases consistently across reporting jurisdictions, and should not be used by providers to determine how to meet a patient’s needs.
Case Definition
This is the official CDC organization who develops national case definitions for National Notifiable Disease Surveillance System
Council of State Territorial Epidemiologists (CSTE)
Type of case which involves a change in individual/group from well to ill (new case)
Incident Case(s)
Type of case that includes all existing cases; current status of an individual or group whether ill or recovered (has or had disease)
Prevalent Case(s)
Division of one number by another, numbers don’t have to be related (ex: 2:1)
Ratio
Numerator is subset of denominator, often expressed as a percentage
Proportion
Time is an intrinsic part of denominator. This term is most often misused.
Rate
950 out of 1000 motorcycle victims are men
(950/1000)*100= 95%
This is an example of a ____
Proportion
“200 per 100,000 population in 1 year”
This is an example of a ______
Rate
The occurrence of NEW cases of disease in a population over a specified period of time
Incidence
“Attack Rate (AR)=
(NEW cases/population at start of epidemic) * 100”
This is an example of ____
Incidence Proportion
(# of new cases during time interval / population at risk during same time interval) * Constant (ex: 10,000, 100,000, etc)
This is the formula for:
Incidence Rate (IR)
“Persons per year” is the layman’s term for ____
Person Years (PY)
(Number of [new and old cases] at a specific point in time / Total population at risk) * Constant =
Prevalence Rate
If incidence is low but duration of the disease is long, prevalence is relatively _____
high
If incidence is high but duration is short, prevalence is relatively _____
low
This type of map is used for clusters or outbreaks with a limited number of cases or geographical area.
Spot/Area Map
Epi curves use a ______ instead of a line graph
histogram (column format)
If during an outbreak, everyone is exposed over a brief period of time and everyone who becomes ill does so within one incubation period, then the outbreak is classified as a
point-source outbreak (ex: Snow’s cholera data)
**In this type of outbreak, cases occur over more than one incubation period. The histogram shows multiple peaks.
Propagated Outbreak (ex: malaria)
This type of outbreak which displays a histograph with a relatively flat curve is known as a
Common Source Outbreak (limited to no person to person transmission and the length of time of outbreak is long, often because it is from a source that is always present or is not recognized quickly enough for preventative measures to be put into place)(Ex: lyme disease- ticks are the vector, or a contaminated food source causing health issues until the food source is found)
