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Overview of Outbreak Investigations. Goals . The goals of this presentation are to: 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. Goals of an outbreak investigation:

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Overview of Outbreak Investigations

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Overview of Outbreak Investigations


Goals

  • The goals of this presentation are to:

    • 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

  • Goals of an outbreak investigation:

    • To identify the source of illness

    • To guide public health intervention

  • Ways to recognize an outbreak:

    • Routine surveillance activities

    • Reports from clinicians and laboratories

    • Reports from affected individuals


Why investigate an outbreak?

  • Characterize a public health problem

  • Identify preventable risk factors

  • Provide new research insights into disease

  • Train health department staff in methods of public health investigations and emergency response


Steps of an outbreak investigation

  • 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

  • Formulate and test hypothesis

  • Plan and execute additional studies

  • Implement and evaluate control measures

  • 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

  • Confirm laboratory testing

  • Rule out misdiagnoses or laboratory error


Define a case and conduct case finding

  • Develop a specific case definition using:

    • Symptoms or laboratory results

    • Time period

    • Location

  • Conduct surveillance using case definition

    • Existing surveillance

    • Active surveillance (e.g. review medical records)

  • Interview case-patients


Tabulate and orient data

  • Create line listing

  • Person

    • Who was infected?

    • What do the cases have in common?

  • Place

    • Where were they infected?

    • May be useful to draw a map

  • Time

    • When were they infected?

    • Create an epidemic curve


Take immediate control measures

  • If an obvious source of the contamination is identified…institute control measures immediately!


Formulate and test hypothesis

  • Develop hypotheses

    • literature reviews of previous outbreaks

    • interviews of several case-patients

  • Conduct an analytic study to test hypotheses

    • Retrospective cohort study

    • Case-control study


Plan and execute additional studies

Environmental sampling

  • Collect appropriate samples

  • Allow epidemiological data to guide testing

  • If analytic study results are conclusive, don’t wait for positive samples before implementing prevention


Implement and evaluate control measures

  • 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

  • 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

  • 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 Professionals- Investigating 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

  • 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


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