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Essential Steps in Disease Outbreak Investigations

Understand the goals and steps of outbreak investigations, identify sources of illness, and implement control measures. Learn how to verify diagnoses, formulate hypotheses, plan studies, and communicate findings effectively. Enhance your knowledge of public health investigations.

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Essential Steps in Disease Outbreak Investigations

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  1. Overview of Outbreak Investigations

  2. 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

  3. 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

  4. 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

  5. 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

  6. Steps of an outbreak investigation • Formulate and test hypothesis • Plan and execute additional studies • Implement and evaluate control measures • Communicate findings

  7. Steps of an outbreak investigation These steps may occur simultaneously or be repeated as new information is received.

  8. Verify the diagnosis and confirm the outbreak • Confirm laboratory testing • Rule out misdiagnoses or laboratory error

  9. 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

  10. 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

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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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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