Epidemiology terms Flashcards
Endemic/enzootic
Normal amount of disease in a population at a given time
Epidemic/epizootic
When a disease occurs at a level about what is normal for a given population
Pandemic
A pandemic is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of people
Vehicle
inanimate objects (food, water, blood, feces, bedding, etc.)
Prevelance
total # of diseased animals / population of interest
Incidence aka risk
new cases of disease / population at risk
What is an attack rate?
the incidence during an active outbreak
Crude mortality
total # deaths / total population
Cause-specific mortality
of deaths from specific disease / total population
Proportionate mortality
of deaths from specific disease / total # of deaths
Case-fatality rate
of deaths from specific disease / total # of cases of specific disease
Descriptive epidemiology
describe the variations in disease frequency among populations by geographical areas and over time (i.e., person, place, and time).
Vehicle
A non-living thing that carries disease (ie. water, food, fomites)
What is a point source curve
Persons are exposed to the same common source over a brief period of time, such as through a single meal or event attended by all cases; number of cases rise rapidly to a peak and falls off gradually; majority of cases occur within one incubation period.
What is a continuous source curve
Exposure is not confined to one point in time (prolonged over a period of days, weeks or longer); as such, cases are spread over a greater period of time depending on how long the exposure persists; lasts more than one incubation period
What is a propagated source curve
Does not have a common source but instead caused by spread of pathogen from one susceptible person to another; transmission may occur directly (person-to-person) or via an intermediate host; tends to have a series of irregular peaks reflecting the number of generations of infection; multiple peaks separated by approx. one incubation period; e.g., person-to-person spread of shigellosis
What is an intermittent source curve
Similar to continuous but exposure is intermittent; multiple peaks – length: no relation to the incubation period (reflects intermittent times of exposure) e.g., contaminated food product sold over period of time
Vertical transmission
from mother to offspring, typically transplacental, transvaginal, or transmammary
Horizontal transmission
from individual to individual
Reservoir
habitat where a disease agent live, grows, and multiplies
What type of study can determine incidence?
Cohort
What type of study can determine prevelance?
Cross-sectional
Relative risk equation
(a/(a+b)) / (c/(c+d))
Relative risk assesses…
risk of developing disease between exposed and non-exposed groups
RR < 1
negative association, aka protective
RR = 1
no association, aka null
RR > 1
positive association, aka risk factor
Odds ratio equation
(a * d) / (b * c)
Odds ratio assess….
risk of having a disease based on exposure
OR < 1
negative association, akak protective
OR = 1
no association, aka null
OR > 1
positive association, aka risk factor
