Epidemiology Flashcards
When is it considered a disease outbreak?
An epidemic confined to a localized area, such as a town or day care center.
What is an attack rate?
Cumulative incidence rate
The usual frequency of a disease is ?
Endemic level
How is it determined to be an epidemic?
Compare it’s frequency in a given population, time, and place to the endemic level
What is a disease cluster?
An occurrence of a group of cases, usually an uncommon disease in a time whose distribution is believed not to be due to chance.
Basic steps in investigating a disease outbreak
- Verify the existence
- Confirm the diagnosis
- Prepare a case definition and count the cases
- Characterize the data
- Formulate and test hypothesis
- Prepare a written report, conduct control, find prevention
Attack rate equation
of new cases occurring among a specified population during a given time period / population at risk at the beginning of the time period x 10^n
What is an epidemic curve?
A graphic representation of the case distribution by time of onset
What are epidemic curves used for?
Constructed for the outbreak as a whole
What are the 3 basic types of disease outbreaks or epidemics?
Common source, propagated, and mixed
What is a common source outbreak?
An outbreak that results from the exposure of a susceptible group of people to a common agent of disease
What is a vehicle in a common source outbreak?
An inanimate object that is capable of transmitting an agent of disease to a susceptible host (food, bedding, surgical equipment, etc.)
What is a point source outbreak?
Type of common source outbreak where the duration of exposure is relatively brief and only among those exposed
What is a continuing source outbreak?
Type of common source outbreak where exposure is prolonged beyond a brief period and the exposure is not only among those exposed.
What is an intermittent source outbreak?
Type of common source outbreak where the exposure to the common source is irregular, leaves gaps in the epidemic curve
How to use epidemic curve when assuming the outbreak is over
Go to first case and count backwards the minimum length of incubation period, then go to the last case of the outbreak and count backwards the maximum length of the incubation period
How to figure out incubation period from epidemic curve
Counting forward from the first point of exposure to the last case of the disease on the epidemic curve
What is a propagated outbreak?
Progressive outbreak that is due to person to person transmission or indirect transmission through a vector
What is a mixed outbreak?
Combination of common source and propagated outbreaks, often begin with a common source outbreak then followed by person to person transmission.
What is an index case?
The first case in a defined group to come to the attention of investigators, often the one who has introduced the causative agent
What is a case-control study?
Used when a specific cohort cannot be defined, cases with the disease are compared to a control group to test the hypothesis that the disease is linked to a specific exposure
What is a retrospective cohort study?
Individuals in a cohort who were exposed are compared to those in the cohort who were not exposed to determine if the factor is linked to the disease
True/False-Retrospective cohort studies use attack rate tables for analysis of disease outbreak
True
For foodborne illness outbreaks, attack rate tables can help determine ?
Which food is likely responsible
