Outbreak investigation


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Outbreak investigation

  1. 1. Dr. Faisal Al Haddad Consultant of Family Medicine
  2. 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. 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. 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. 5. Steps of an outbreak investigation 1. Verify the diagnosis and confirm the outbreak 2. Define a case and conduct case finding 3. Tabulate and orient data: time, place, person 4. Take immediate control measures 5. Formulate and test hypothesis
  6. 6. Steps of an outbreak investigation 6. Plan and execute additional studies 7. Implement and evaluate control measures 8. Communicate findings N.B. These steps may occur simultaneously or be repeated as new information is received.
  7. 7. Step 1: Verify the diagnosis and confirm the outbreak  Verifying the existence of a true outbreak is critical to proceeding with an investigation.  Confirmation of the diagnosis with a laboratory is important. Without confirmation, the situation may become a “pseudo-outbreak,”  Rule out misdiagnoses or laboratory error
  8. 8. Step 2: 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
  9. 9. Step 3: 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
  10. 10. Step 4: Take immediate control measures If an obvious source of the contamination is identified…institute control measures immediately!
  11. 11. Step 5: 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
  12. 12. Step 6: 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
  13. 13. Step 7: 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
  14. 14. Step 8: 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
  15. 15. 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.
  16. 16. QUESTION 1 During the investigation of an outbreak of food poisoning at a summer camp, food histories were obtained from all campers as indicated in the following table. Which of the food items was probably responsible for the outbreak?
  17. 17. QUESTION 2 Which one of the following is LEAST helpful in the investigation of an outbreak of suspected food poisoning? 1. Culture of vomitus of affected persons 2. Culture of feces of affected persons 3. Rapid identification of cases 4. Collection of samples of food eaten 5. Identification of foods consumed by individuals
  18. 18. 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
  19. 19. THANK YOU