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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. - PowerPoint PPT Presentation
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Rendi Murphree, PhDCDC Epidemic Intelligence Service Officer
Tennessee Department of Health
Council of State and Territorial Epidemiologists Annual Meeting
June 13, 2011
Characteristics of Foodborne Disease Outbreak Investigations Conducted by
FoodNet Sites, 2003–2008
Office of Surveillance, Epidemiology, and Laboratory ServicesScientific Education and Professional Development Program Office
BACKGROUNDFoodNet Outbreak Investigations
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)7-15CDC, Foodborne Outbreak Online Database, http://wwwn.cdc.gov/foodborneoutbreaks Accessed 28 June 2010.
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
Foodborne Disease OutbreakSurveillance Systems
CDC Foodborne Disease Outbreak Surveillance System NORS All states
Foodborne Disease Active Surveillance Network FoodNet 10 states
OBJECTIVESFoodNet Outbreak Investigations
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
METHODSFoodNet Outbreak Investigations
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
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
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
RESULTSFoodNet Outbreak Investigations
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
FBDO by Year — FoodNet Sites, 2003–2008N = 1,200
FBDO Characteristics — FoodNet Sites, 2003–2008
All 10 Sites
Number reported 1,200
Average annual rate per million 4
Confirmed etiology (%) 50
Food vehicle identified (%) 32
Etiology & food vehicle identified (%)
20
FBDO Characteristics — FoodNet Sites, 2003–2008
All 10 Sites Range
Number reported 1,200 11–279
Average annual rate per million 4 1–9
Confirmed etiology (%) 50 37–82
Food vehicle identified (%) 32 16–50
Etiology & food vehicle identified (%)
20 7–39
FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–
2008 (n = 715)
FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–
2008 (n = 715)
FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–
2008 (n = 715)
FBDO Seasonality by Confirmed Etiology — FoodNet Sites, 2003–
2008 (n = 715)
02468
10121416
Prop
ortio
n
Month of First Illness Onset
Bacterial Etiology Viral Etiology Unknown Etiology
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)
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
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
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
FBDO Characteristics by Outbreak Size — FoodNet Sites, 2003–2008
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)
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
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)
Source of Initial FBDO Recognition —
FoodNet Sites, 2003–2008Viral
n = 471Bacterialn = 246
No. (%) No. (%)
Private citizen 363 (87) 80 (33)
Reportable disease surveillance 11 ( 3) 75 (30)
Medical professional report 34 ( 8) 43 (17)
DNA match 0 ( 0) 33 (13)
Syndromic surveillance 0 ( 0) 3 ( 1)
Other 10 ( 2) 12 ( 5)
Source of Initial FBDO Recognition —
FoodNet Sites, 2003–2008Viral
n = 471Bacterialn = 246
No. (%) No. (%)
Private citizen 363 (87) 80 (33)
Reportable disease surveillance 11 ( 3) 75 (30)
Medical professional report 34 ( 8) 43 (17)
DNA match 0 ( 0) 33 (13)
Syndromic surveillance 0 ( 0) 3 ( 1)
Other 10 ( 2) 12 ( 5)
Source of Initial FBDO Recognition —
FoodNet Sites, 2003–2008Viral
n = 471Bacterialn = 246
No. (%) No. (%)
Private citizen 363 (87) 80 (33)
Reportable disease surveillance 11 ( 3) 75 (30)
Medical professional report 34 ( 8) 43 (17)
DNA match 0 ( 0) 33 (13)
Syndromic surveillance 0 ( 0) 3 ( 1)
Other 10 ( 2) 12 ( 5)
n = 370
Receipt of Initial FBDO Recognition—
FoodNet Sites, 2006–2007
Settings of FBDO — FoodNet Sites, 2003–2008
Site of food preparation (n = 1,088) 64% restaurant or deli 7% caterer
11% home
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
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
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
DISCUSSIONFoodNet Outbreak Investigations
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
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
Conclusions & Recommendations Public health agencies must improve investigation
of foodborne disease outbreaks
Recommendations Systematically review complaints from the public Increase stool specimen collection
o Health departments o Clinicians
Consider new methods for identifying and contacting patients and control subjects
Provide training o Conducting epidemiologic studieso Collecting NORS and FoodNet data
For more information please contact Centers for Disease Control and Prevention1600 Clifton Road NE, Atlanta, GA 30333Telephone, 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348E-mail: cdcinfo@cdc.gov Web: www.cdc.govThe findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
AcknowledgementsFoodNet Partners 10 states CDC, FDA, USDA
EIS Supervisory Team Timothy F. Jones John R. Dunn William Schaffner W. Randolph Daley
Coauthors Katie Garman Quyen Phan Karen Everstine L. Hannah Gould Timothy F. Jones
Office of Surveillance, Epidemiology, and Laboratory ServicesScientific Education and Professional Development Program Office
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