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Epi exam 2
outbreak investigations
| Question | Answer |
|---|---|
| why do we conduct outbreak investigations? | - to institute control and prevent further outbreaks |
| Reasons for conducting outbreak investigations: | - opportunity for research and training - public relations - political concerns - legal obligations |
| when do we conduct an outbreak investigation? | when cases are approaching epidemic status |
| what are the 10 steps for conducting an outbreak investigation? | 1. prepare for field work 2. establish the existence of an outbreak 3. verify the diagnosis 4. define and identify cases 5. perform descriptive epidemiology 6. develop hypothesis 7. evaluate hypotheses 8. refine hypotheses 9. implement control or |
| what are the 3 categories for preparing for field work? | |
| how do cases come to the attention of the health department? | - regular analysis of surveillance data - calls from a health care provider - from the public (interesting cases) - from local media |
| what is the definition of an outbreak? | occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time |
| what is the difference between an outbreak and an epidemic? | epidemics are typically ongoing and not easily solved. outbreaks are more short term |
| what is the definition of cluster? | aggregation of cases in a given area over a period without regard to whether the number of cases is more than expected |
| what are ways that we can compare observed data with expected cases? | - health department data - locally existing data - apply rates from neighboring states |
| how do we verify the diagnosis of an outbreak investigation? | - establish what event is occurring and the outcome - summarize the clinical finding with frequency distributions |
| what are frequency distributions useful for? | useful in characterizing the spectrum of illness |
| what is a case definition? | set of criteria to determine what classifies as a case and what does not |
| when verifying the diagnosis what are some things you should ask patients? | - what were your exposures before becoming ill? - what do they think caused their illness? - do they know anyone else with the disease? |
| what do conversations with patients help the researcher develop? | help to develop hypotheses about the outcome, etiology, and spread |
| what do case definitions include? | - person, place, and time - clinical criteria - setting of the outbreak (place) - date (day) and time of the event (time) |
| what can case definitions restrict by? | - by person (individuals in a certain department) - place (state, county, country) - time (within the past 3 weeks) |
| what are not included in case definitions? | the exposure |
| what is important when determining cases? | - that exposures are not included in the case definition - criteria is applied consistently and without bias |
| what are the different classifications of cases when there is uncertainty? | - probable - possible - suspect |
| what does descriptive epidemiology do? | describes data (events) |
| how are events described? | - number of people ill - number exposed - number in attendance - incidence and prevalence calculations - attack rates - epidemic curves |
| what is an epidemic curve? | a graphical depiction of the number of cases of illness |
| what does the x- axis of an epidemic curve represent? | illness onset |
| what does the y-axis of an epidemic curve represent? | # of cases |
| what is the purpose of epidemic curves and what do they tell us? | - pattern of spread - magnitude - outliers - time trend (how long is it going on) - exposure and/or disease incubation period |
| what does the shape of an epidemic curve reveal? | the type of outbreak |
| how are epidemic curves interpreted? | - consider overall shape |
| what is the shape of epidemic curves determined by? | the period of time over which susceptible persons are exposed |
| how to make an epidemic curve: | - plot the number of cases of disease reported during an outbreak on the y-axis - plot the time or date of illness onset on the x-axis |
| what does the time unit for the x-axis depend on? | the incubation period for the disease |
| do we need to know the incubation period to create an epidemic curve? | no |
| what are the types of epidemic curves? | continuous or intermittent |
| what are common source outbreaks? | outbreak that results from the exposure of a susceptible group of people to a common agent of disease |
| what are common source intermittent exposure? | results in an epi curve with irregular peaks that reflect the timing and the extent of exposure |
| what do common source intermittent curves produce? | little epi curves within a big one |
| what is common source continuous exposure? | often cause cases to rise gradually and goes on until it is discovered, these have a plateau rather than a peak |
| what is a common source point source? | a common source outbreak where the period of exposure is brief and all cases occur within one incubation period |
| what does a common source point curve look like? | a sharp upward slope and a gradual downward slope |
| what type of transmission causes common source outbreaks? | indirect transmission |
| what type of transmission causes propagated outbreaks? | direct transmission |
| what are the characteristics of a propagated epi curve? | - it is spread person to person - can last longer than common source outbreaks - may have multiple waves |
| why are outbreak investigations conducted? | to learn more about an outbreak |
| what are some constraints in doing outbreak investigations? | - time constraints - concerns from the public - power - public attention - bias |
Created by:
kenzieblair8