2011 Hyla Middle School Science Talk

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Foodborne illness attorney Bill Marler speaks to a Hyla Middle School Science about how food poisoning outbreaks are investigated

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2011 Hyla Middle School Science Talk

  1. 1. Hyla MiddleSchool ScienceMaking the CausalLink: InvestigatingFoodborne DiseaseOutbreaksWilliam D. Marler, Esq.
  2. 2. CDC Estimates of Foodborne Illness • 48 million cases of foodborne illness annually • 125,000 hospitalizations • 3,000 deaths
  3. 3. Estimates Differ From Actual Counts• Annual E. coli O157 estimates – 62,000 illnesses – 1,800 hospitalizations – 52 deaths• But, only 2,621 E. coli 0157 cases were reported in 2005
  4. 4. Notifiable/Reportable Diseases • Reporting authorized by Congress in 1878 • Nationally Reportable Diseases - 1993 (food or water borne origin) Botulism, Cryptosporidiosis, Cyclosporiasis, Giardiasis, Hemolytic Uremic Syndrome (post-diarrheal), Hepatitis A, Listeriosis, Salmonellosis, Shiga toxin producing Escherichia coli (STEC), Shigellosis, Trichinosis, Vibriosis http://www.cdc.gov/ncphi/disss/nndss/phs/infdis2008.htm
  5. 5. Pathway of a Foodborne IllnessInvestigation
  6. 6. Pathway of a Foodborne IllnessInvestigation If there are more ill persons than expected, an OUTBREAK might be underway.
  7. 7. How Do We Know If There Is an Excess? Public Health Surveillance The ongoing collection, analysis, interpretation and dissemination of health data directed towards the control and prevention of diseases.
  8. 8. Pathway of a Foodborne IllnessInvestigation
  9. 9. Typical Steps of an OutbreakInvestigation• Verify the diagnosis• Establish that an outbreak is occurring• Define and identify cases• Orient the data in terms of person, place, and time• Develop and test the hypotheses• Case Control Study• Refine the hypotheses and carry out additional studies• Implement control and prevention measures• Report findings
  10. 10. A Word to the Wise! • No mandatory list of how to proceed • No set order of steps to take • Investigation is dynamic: case definition, line listings, descriptive epidemiology, hypotheses can change • Expect the unexpected
  11. 11. Investigative Partners • Laboratory investigators – Microbiologic diagnosis – Virology/Parasitic Labs – Molecular analysis • Epidemiologic investigators – Individual case interviews – Outbreak investigation • Cohort studies • Case/control studies • Environmental investigators – Facility investigation – Environmental sampling – Product traceback
  12. 12. Epidemiology–Basic Tools of the TradeReal-time interviewing with a broad-basedexposure questionnaire • Symptoms • Incubation • Duration • Food History • Medical Attention • Suspected source • Others Ill
  13. 13. Pulsed Field Gel Electrophoresis (PFGE)A Powerful Outbreak Detection Tool • Process separates chromosomal fragments of intact bacterial genomic DNA grown from patient isolate • Results in 10 to 20 DNA fragments which distinguish bacterial strains • Genetic relatedness among strains is based on similarities of the DNA patterns • Outbreak strains are those that are epidemiologically linked AND genetically linked
  14. 14. Questions to Consider in AssessingPFGE Clusters• How common is the PFGE subtype?• How many cases are there?• Over what time frame did cases occur?• What is the geographic distribution of cases?• What are the case demographics?• Do any of the cases have a “red flag” exposure?
  15. 15. E. coli O157:H7 Outbreak, Minnesota, September 2005 Thanks to MN DOH “Team D” for use of the following slides!Team Diarrhea
  16. 16. Outbreak Detection September 27, 2005 • Three O157 isolates with indistinguishable PFGE patterns identified by Minnesota Public Health Laboratory • PFGE pattern new in Minnesota, rare in United States – 0.35% of patterns in National Database • Patients reported eating prepackaged salad; no other potential common exposures evident
  17. 17. E. coli O157:H7 Cases Associatedwith Dole Prepackaged Lettuce 7Number of Cases 6 5 4 3 2 Initial cluster of 3 isolates among MN residents 1 identified. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 September October Date of Onset 2005
  18. 18. Outbreak Investigation - Methods September 28–29, 2005 • Additional O157 isolates received at the MDOH and subtyped by PFGE – 7 isolates demonstrated outbreak PFGE subtype • Supplemental interview form created • Case-control study initiated
  19. 19. E. coli O157:H7 Cases Associatedwith Dole Prepackaged Lettuce 7Number of Cases 6 5 4 Case-control study initiated. 3 2 Initial cluster of 3 isolates among MN residents 1 identified. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 September October Date of Onset 2005
  20. 20. Case-Control Study ResultsExposure Cases Controls Matched OR* 95% CI† p-valueAny lettuce 9/10 17/26 3.5 0.5–25.0 0.17Prepackagedlettuce salad 9/10 10/26 8.4 1.2–59.6 0.01Doleprepackagedlettuce salad 9/10 5/23 10.1 1.5–67.3 0.002*OR = odds ratio† CI = confidence interval
  21. 21. E. coli O157:H7 Cases Associatedwith Dole Prepackaged Lettuce 7Number of Cases 6 5 Case-control study implicated Dole salad. 4 Case-control study initiated. 3 2 Initial cluster of 3 isolates among MN residents 1 identified. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 September October Date of Onset 2005
  22. 22. E. coli O157:H7 Cases Associatedwith Dole Prepackaged Lettuce CDC, FDA notified. 7Number of Cases 6 5 Case-control study implicated Dole salad. 4 Case-control study initiated. 3 2 Initial cluster of 3 isolates among MN residents 1 identified. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 September October Date of Onset 2005
  23. 23. E. coli O157:H7 Cases Associatedwith Dole Prepackaged Lettuce CDC, FDA notified. 7Number of Cases 6 5 Case-control study implicated Dole salad. 4 Case-control study initiated. 3 2 Initial cluster of 3 isolates among MN residents 1 identified. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 September October Date of Onset 2005
  24. 24. E. coli O157:H7 Cases Associated withDole Prepackaged Lettuce (N=26) Minnesota Additional statesNumber of Cases 7 6 5 OR 4 3 2 WI 1 WI 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 September October Date of Onset 2005
  25. 25. Dole Classic Romaine Salad Recoveredfrom Case-Households Shared common "Best if Used By” Date and production code
  26. 26. Product Traceback • Single processing plant (Soledad, CA) • Production Date of September 7, 2005 • Lettuce harvested from any 1 of 7 fields
  27. 27. PFGE Patterns of E. coli O157:H7Isolates from Lettuce Source Initial Minnesota Case-patient Classic Romaine Bag #1 Classic Romaine Bag #2
  28. 28. Why Epidemiologic Links May Not beIdentified for Cases in a PFGE Cluster • Cases have imperfect recall • Common exposures can be difficult to link (e.g., eggs, chicken) • Secondary transmission • Cross-contamination exposure • There isn’t a common source
  29. 29. CDC 2005 Cluster Investigations E. coli O157 SalmonellaPatterns Submitted 5,376 29,168Clusters Identified 67 176Multi-state Clusters 36 152Epi Investigation 19 30Vehicle Implicated 4 8Regulatory Activity 4 8
  30. 30. Questions?

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