Morbidity and Mortality Flashcards
Commonly Used Measures of Morbidity
incidence
incidence density
attack rates
prevalence
R0 (r-naught)
BASIC Reproduction Number (or reproductive rate), inherent of the agent and determines how a disease can spread through a population (important for herd immunity)
new cases over initial cases
Relationship between R0 and the infectiousness of an agent
larger R0 = more infectious agent
R
EFFECTIVE reproduction number, or the average number of cases generated by a single case in both susceptible and non-susceptible populations
R>1
sustained trasnmission
R<1
infection will die out
Do disease control interventions affect R or R0?
R (remember R0 is inherent to the agent)
Which is most common in epi - ratio, proportion, or rate?
Rate (relative frequency) - because it is based on counts (discrete data) and can be used in diagnostics and interventions
4 Components Rate
- Frequency (numerator)
- Population at Risk (denominator)
- Time period (ETC and ITC)
- Location
ETC (External Time Component)
length of time study was carried out
ITC (Internal Time Component)
per unit of time to which a specific rate applies
Incidence Rate
measure of rate
Incidence Density
used when the entire population at risk is not observed through the entire defined period (ex: 5.7 cases per 100 calf months)
Primary Attack Rate
number of those ill/
number in exposure group being assessed
Secondary Attack Rate
true population at risk = total pop. minus the primary cases
Which is a measure of pathogen infectivity - primary or secondary attack rate?
Secondary Attack rate
Main assumption of secondary attack rate?
all secondary cases caught the disease from the primary cases
Prevalence
proportion
What type of study is used to determine prevalence of disease?
cross-sectional (and case control)
Label the bathtub.
incidence, prevalence, recurrence, mortality
What types of studies use incidence?
clinical trials and cohort
Mortality Rate
number of deaths/population at risk (can be overall or specific)
Case Fatality Rate
What is case fatality rate a measure of?
virulence
Measure of Association with Cross Sectional and Case Control Studies (Prevalence) (Retrospective)?
Odds Ratio
Measure of Association with Cohort and Clinical Trial Studies (Incidence) (Prospective)?
Relative Risk
Relationship Between Prevalence and Incidence in Rapidly Fatal Cases?
incidence will be higher than prevalence
Mathematical Equation describing the relationship between Incidence, Prevalence, and Duration of Disease?
Is prevalence more relevant in acute or chronic?
chronic (in acute, will be fairly equal to incidence)
