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Characteristics of Foodborne Disease Outbreak Investigations Conducted by FoodNet Sites, 2003–2008

Characteristics of Foodborne Disease Outbreak Investigations Conducted by FoodNet Sites, 2003–2008. Rendi Murphree, PhD. CDC Epidemic Intelligence Service Officer Tennessee Department of Health Council of State and Territorial Epidemiologists Annual Meeting June 13, 2011.

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Characteristics of Foodborne Disease Outbreak Investigations Conducted by FoodNet Sites, 2003–2008

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  1. Characteristics of Foodborne Disease Outbreak Investigations Conducted by FoodNet Sites, 2003–2008 Rendi Murphree, PhD CDC Epidemic Intelligence Service Officer Tennessee Department of Health Council of State and Territorial Epidemiologists Annual Meeting June 13, 2011 Office of Surveillance, Epidemiology, and Laboratory Services Scientific Education and Professional Development Program Office

  2. FoodNet Outbreak Investigations BACKGROUND

  3. Annual Burden of Foodborne Illness and Outbreaks in the United States Foodborne illnesses (estimated) 9.4 million illnesses 1,351 deaths 31 major pathogens Foodborne outbreaks (reported) 20,000 illnesses 20 deaths Investigations identify factors contributing to foodborne illness Etiology and food vehicle often unknown Scallan et al., Foodborne illness acquired in the United States, Emerg Infect Dis, 2011, Jan 7(1)7-15 CDC, Foodborne Outbreak Online Database, http://wwwn.cdc.gov/foodborneoutbreaksAccessed 28 June 2010.

  4. Foodborne Disease OutbreakSurveillance Systems • CDC Foodborne Disease Outbreak Surveillance System • NORS (National Outbreak Reporting System) • All states • Outbreak characteristics • Foodborne Disease Active Surveillance Network • FoodNet • 10 states, CDC, FDA and USDA • ~45 million people; 15% of the U.S. population • Supplemental data on investigation characteristics

  5. Foodborne Disease OutbreakSurveillance Systems • CDC Foodborne Disease Outbreak Surveillance System • NORS • All states • Foodborne Disease Active Surveillance Network • FoodNet • 10 states

  6. OBJECTIVES FoodNet Outbreak Investigations

  7. Study Objectives Summarize data on FoodNet outbreak investigations Determine factors associated with identifying an etiology and implicating a food vehicle Describe barriers to successful investigations Recommend investigation improvements

  8. METHODS FoodNet Outbreak Investigations

  9. Data Source FoodNet sites CT, GA, MD, MN, OR, TN Counties in CA, CO, NY NM since 2004 2003–2008 Multi-state outbreaks excluded Combined NORS and FoodNet data

  10. Variables NORS Form Information on the outbreak FoodNet Outbreak Supplement Form Information on the outbreak investigation Recognition and reporting Investigation design Specimen testing Barriers impeding the investigation

  11. Definitions Foodborne disease outbreak (FBDO) ≥2 cases of a similar illness resulting from the ingestion of a common food Food vehicle identified Statistical evidence or laboratory evidence Etiology confirmed CDC criteria Odds ratios adjusted for outbreak size *Olsen, et al., MMWR Surveillance Summary, 2000;49(1):1-62

  12. RESULTS FoodNet Outbreak Investigations

  13. FBDOs — FoodNet Sites, 2003–2008 42 multi-state outbreaks excluded 1,200 outbreaks analyzed Annual mean number = 200 (range 117–253) 18,593 illness caused by 1,111 outbreaks Mean = 17 per outbreak (range 2–273) Marked variability in outbreak frequency and investigation characteristics

  14. FBDO by Year — FoodNet Sites, 2003–2008N = 1,200

  15. FBDO Characteristics — FoodNet Sites, 2003–2008

  16. FBDO Characteristics — FoodNet Sites, 2003–2008

  17. FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–2008 (n = 715)

  18. FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–2008 (n = 715)

  19. FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–2008 (n = 715)

  20. FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–2008 (n = 715)

  21. Stool Key to Confirming an Etiology Stool specimens obtained in 89% of 715 outbreaks with a confirmed etiology vs. 48% of 485 without Odds ratio = 9.2 (6.8–12.3)

  22. Stool obtained in 89% of 715 outbreaks with a confirmed etiology vs. 48% of 485 without Odds ratio = 9.2 (6.8–12.3) Odds of confirming an etiology did not improve with the collection of >4 stool specimens Odds ratio = 7.2 (4.9–10.6) Stool Key to Confirming an Etiology

  23. Stool obtained in 89% of 715 outbreaks with a confirmed etiology vs. 48% of 485 without Odds ratio = 9.2 (6.8–12.3) Odds of confirming an etiology did not improve with the collection of >4 stool specimens Odds ratio = 7.6 (5.3–10.9) Proportion of outbreaks with a confirmed etiology high, regardless of interval between symptom onset and stool collection Median 0–3 days (70%), 4–7 days (78%), 8–14 days (69%) Stool Key to Confirming an Etiology

  24. Stool obtained in 89% of 715 outbreaks with a confirmed etiology vs. 48% of 485 without Odds ratio = 9.2 (6.8–12.3) Odds of confirming an etiology did not improve with the collection of >4 stool specimens Odds ratio = 7.6 (5.3–10.9) Proportion of outbreaks with a confirmed etiology high, regardless of interval between symptom onset and stool collection Median 0–3 days (70%), 4–7 days (78%), 8–14 days (69%) Stool Key to Confirming an Etiology

  25. FBDO Characteristics by Outbreak Size — FoodNet Sites, 2003–2008

  26. Keys to Implicating a Food Vehicle Food vehicle implicated in 47% of 671 outbreaks investigated using a case-control or cohort study vs. 14% of 529 using other methods Odds ratio = 4.9 (3.6–6.7)

  27. Keys to Implicating a Food Vehicle Food vehicle implicated in 47% of 671 outbreaks investigated using a case-control or cohort study vs. 14% of 529 using other methods Odds ratio = 4.9 (3.6–6.7) Analytic study conducted in only 20% of outbreaks causing 2–4 illnesses

  28. Keys to Implicating a Food Vehicle Food vehicle implicated in 47% of 671 outbreaks investigated using a case-control or cohort study vs. 14% of 529 using other methods Odds ratio = 4.9 (3.6–6.7) Analytic study conducted in only 20% of outbreaks causing 2–4 illnesses Food specimens collected in 91 (36%) of 253 investigations successful in identifying a food vehicle Odds ratio = 4.9 (3.6–6.7)

  29. Source of Initial FBDO Recognition — FoodNet Sites, 2003–2008

  30. Source of Initial FBDO Recognition — FoodNet Sites, 2003–2008

  31. Source of Initial FBDO Recognition — FoodNet Sites, 2003–2008

  32. Receipt of Initial FBDO Recognition— FoodNet Sites, 2006–2007 n = 370

  33. Settings of FBDO — FoodNet Sites, 2003–2008 Site of food preparation (n = 1,088) 64% restaurant or deli 7% caterer 11% home

  34. Preparation Leading to FBDO — FoodNet Sites, 2008 Timing of contamination (n = 129) 74% at the time of preparation or serving 26% prior to final preparation Contaminated food served (n = 184) 86% single establishment or event

  35. Agencies Involved in FBDO Investigations — FoodNet Sites, 2003–2008 37% local health departments only 47% local and state agencies 5% local, state and federal agencies Local health departments not involved in 12% n = 1,185

  36. Barriers Affecting FBDO Investigations — FoodNet Sites, 2003–2008 Notification 18% delayed notification of local health departments Cases 26% too few cases 24% lack of cooperation from cases Controls 23% too few controls 10% inability to identify good controls for an analytic study Stool 25% too few stool specimens n = 655

  37. DISCUSSION FoodNet Outbreak Investigations

  38. Overview of Major Findings FBDOs: Mainly recognized and handled locally Attributed to exposures outside the home Caused by contamination at time of preparation Stool specimens key to confirming an etiology At least 4 Stool collection weeks after symptom onset useful Analytic study best for implicating a food vehicle Cohort or case-control study Food specimen collection rare but helpful in bacterial outbreaks

  39. Study Limitations Data quality Incomplete data submitted to CDC Questions changed over time Subjective interpretation No ongoing training for data collectors Some data not reported by staff directly involved in the outbreak investigation Results May not be generalizable to non-FoodNet sites

  40. Conclusions & Recommendations Public health agencies must improve investigation of foodborne disease outbreaks Recommendations Systematically review complaints from the public Increase stool specimen collection Health departments Clinicians Consider new methods for identifying and contacting patients and control subjects Provide training Conducting epidemiologic studies Collecting NORS and FoodNet data

  41. Acknowledgements FoodNet Partners 10 states CDC, FDA, USDA EIS Supervisory Team Timothy F. Jones John R. Dunn William Schaffner W. Randolph Daley • Coauthors • Katie Garman • QuyenPhan • Karen Everstine • L. Hannah Gould • Timothy F. Jones Office of Surveillance, Epidemiology, and Laboratory Services Scientific Education and Professional Development Program Office

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