Descriptive Epi Chapter 2 Flashcards
Fixed/Dynamic Population
- fixed:a permanent membership. (WWII vets)
- dynamic: able to change (city population is dynamic, people move in/out of boundary)
Steady State
people entering=people leaving
What factors should be considered when measuring how common a disease presents in pop.?
- number of people affected by disease
- size of pop. from where the disease cases arise
- how long pop. is followed
What do you use to measure and compare disease occurrence?
- ratios: 4/2 # divided by #
- rates:division of two numbers. Time is in denominator
- proportions:division of related numbers.
How to measure disease frequency?
- incidence:occurrence of new disease over a period of time.
- prevalence:proportion of total population that is diseased
candidate population
people who are “at risk” for getting disease
Cumulative Incidence
-proportion of "at risk" population that become diseased over set time. # new cases/ # "at risk" with time frame
Incidence Rate
occurrence of new cases of disease that arise during person-time of observation.
True rate as time is incorporated into the denominator.
What measures the transition from health to disease?
- cumulative incidence: useful for fixed.
- incidence rate: useful for dynamic populations.
Point prevalence
-proportion of pop. diseased at a single point in time
total pop.
Period prevalence
-proportion of pop. diseased over set time frame.
What are incidence and prevalence used for?
- incidence:evaluate effectiveness of program to prevent disease.
- prevalence: obscures causal relationships, bc in combines incidence and survival.
Crude Mortality Rate
Total number of deaths from all causes/100,000/ 1yr
Cause-specific Mortality Rate
of deaths from specific cause/100,000/ 1yr
Natality (live birth rate)
of livebirths/ 1,000/ 1yr
Infant Mortality Rate
deaths of infants
Morbidity Rate
of existing or new cases of a particular disease per 100 people
Attack Rate
of new cases of disease that develop
———————————————- for time period
“healthy at risk”
Similar to Incidence Proportion
Case Fatality Rate
of deaths per # of disease cases
type of cumuulative incidence. MUST specify time frame
Survival Rate
of living cases of disease
complement to case fatality rate
cumulative incident measure
Catchment Population
Number of people that use a facility’s service
Descriptive Epidemiology
-used to determine if a site/location is experiencing disease occurrence more frequently than usual
Passive Surveillance System
Relies on healthcare to follow regulations to report diseases
Active Surveillance Sustem
Send officials into community to search for new disease case
Syndromic Surveillance System
Observes pre-defined sings of patients that need reported or evaluated
What is a “case” definition?
Uniform criteria that define a disease
- allows for consistent classification and reporting of cases
- can vary by state
- are updated annually
Epidemic
- cases of disease that greatly exceed normal expectancy
- clearly define community, time period
- goal: capture disease ASAP
Outbreak
- epidemic limited to a localized increase in occurrence of disease
- similar to cluster
Endemic
-constant presence of disease in given area or population greater than other areas
Pandemic
- epidemic that occurs over wide range, involving many people
- multi region or national
Epidemic Curve
- depiction of outbreak/epidemic cases by date
- demonstrates the pattern of spread
- depicts magnitude of impact
Common Source
Derived from a single point and spread
Propagated Source
Spread person-to-person
