Download Overview of Outbreak Investigations

Overview of Outbreak
Investigations
Goals
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The goals of this presentation are to:
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Provide a general overview of the
basic steps of disease outbreak
investigations
Describe factors that may contribute
to a decision to investigate
Outbreaks: The basics
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Goals of an outbreak investigation:
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To identify the source of illness
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To guide public health intervention
Ways to recognize an outbreak:
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Routine surveillance activities
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Reports from clinicians and laboratories
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Reports from affected individuals
Why investigate an outbreak?
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Characterize a public health problem
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Identify preventable risk factors
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Provide new research insights into disease
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Train health department staff in methods of
public health investigations and emergency
response
Steps of an outbreak
investigation
1.
2.
3.
4.
Verify the diagnosis and confirm the
outbreak
Define a case and conduct case
finding
Tabulate and orient data: time, place,
person
Take immediate control measures
Steps of an outbreak
investigation
5.
Formulate and test hypothesis
6.
Plan and execute additional studies
7.
Implement and evaluate control
measures
8.
Communicate findings
Steps of an outbreak
investigation
These steps may occur
simultaneously or be repeated as
new information is received.
Verify the diagnosis and
confirm the outbreak

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Confirm laboratory testing
Rule out misdiagnoses or laboratory
error
Define a case and conduct
case finding
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Develop a specific case definition using:
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Conduct surveillance using case definition
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Symptoms or laboratory results
Time period
Location
Existing surveillance
Active surveillance (e.g. review medical records)
Interview case-patients
Tabulate and orient data
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Create line listing
Person
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Place
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Who was infected?
What do the cases have in common?
Where were they infected?
May be useful to draw a map
Time
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When were they infected?
Create an epidemic curve
Take immediate control
measures
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If an obvious source of the
contamination is identified…institute
control measures immediately!
Formulate and test hypothesis
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Develop hypotheses
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literature reviews of previous outbreaks
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interviews of several case-patients
Conduct an analytic study to test
hypotheses
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Retrospective cohort study
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Case-control study
Plan and execute additional
studies
Environmental sampling
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Collect appropriate samples
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Allow epidemiological data to guide testing
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If analytic study results are conclusive,
don’t wait for positive samples before
implementing prevention
Implement and evaluate
control measures
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Prevent further exposure and future
outbreaks by eliminating or treating the
source
Work with regulators, industry, and
health educators to institute measures
Create mechanism to evaluate both
short- and long-term success
Communicate findings
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Identify a single member of the
investigation team to interact with
media and communicate progress and
findings
Summarize investigation, make
recommendations, and disseminate
report to all participants
Conclusions
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
The steps listed for an outbreak investigation
comprise a brief introduction and rough
guide. Only by conducting investigations
repeatedly over an entire career will public
health professionals truly learn the methods
of outbreak investigations.
Snow’s “shoe leather epidemiology” serves as
a model of critical thinking and public health
action.
Online resources

Information for Public Health ProfessionalsInvestigating Foodborne Disease Outbreaks. Available
online at:
http://www.cdc.gov/foodborneoutbreaks/info_healthprofessional
.htm

To conduct an online outbreak investigation,
“Botulism in Argentina,” visit the CDC website at:
http://www.phppo.cdc.gov/phtn/casestudies/
computerbased/default.htm

To explore an historical outbreak investigation, visit
the online UNC John Snow Case Study at:
http://www.sph.unc.edu/courses/Course_support/
Case_studies/John Snow
References
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Michael Gregg. Field Epidemiology. 2nd
edition. Oxford University Press, 2002.
Control of Communicable Disease in Man,
17th edition. Chin, J (ed). APHA, 2000.
Principles & Practice of Infectious Diseases,
5th edition. Mandell GL, Bennett JE, Dolin R
(eds). Churchill Livingstone; 2000