ESTIMATING THE SOURCES OF FOODBORNE ILLNESS IN THE

ESTIMATING THE SOURCES OF FOODBORNE ILLNESS IN THE UNITED STATES Dana Cole, DVM, Ph. D Enteric Disease Epidemiology Branch, Division of Foodborne, Waterborne, and Environmental Diseases January 31 st, 2012 National Center for Emerging and Zoonotic Infectious Diseases Enteric Diseases Epidemiology Branch

Outline • Background and purpose • Where source attribution starts • Painting a clearer picture • Looking forward 2

Outline • Background and purpose –Goal –Questions • Where source attribution starts • Painting a clearer picture • Looking forward 3

“Art and science have their meeting point in method. ” Earl Edward George Bulwer-Lytton (1875) 4

“Art and science have their meeting point in method. ” Earl Edward George Bulwer-Lytton (1875)

Our Overarching Goal To prevent illness and death by gathering and analyzing information to create collective knowledge and stop food problems before they happen 6

Foodborne Illness Source Attribution: What is it? at·tri·bu·tion: [a-trə-byü-shən] 1. The act of attributing, especially the act of establishing a particular person as the creator of a work of art. <The American Heritage® Dictionary of the English Language> 1. The act of attributing, especially specifically the act of establishing a particular person food as the creator source of an work of art infection. 7

Purpose: Inform food safety decision-making q Determine the most pressing food safety priorities q Intervene to reduce illness at points in food chain where intervention can have the greatest impact q Target prevention measures to meet long-term goals q Measure progress toward food safety goals 8 8

Attribution of Illnesses to Food Sources q q We need to use new tools to understand today’s food safety challenges Using these tools, we will paint a clearer picture of foodborne illness source attribution 9

Outline • Background and purpose • Where source attribution starts • Painting a clearer picture • Looking forward 10

Cycle of Foodborne Disease Control and Prevention Surveillance Prevention Measures Epidemiologic Investigation Applied Research 11

Cycle of Foodborne Disease Control and Prevention Surveillance Prevention Measures OUTBREAK Epidemiologic Investigation Applied Research 12

Investigating the Source of Outbreaks q q Escherichia coli O 157 outbreaks in mid 1980’s and early 1990’s traced to ground beef Information used to guide interventions taken by regulatory agencies: • Recommended minimum cooking temperature of hamburgers was raised • Food Safety Inspection Service (FSIS): • Implemented HACCP (Hazard Analysis and Critical Control Points) • Made E. coli O 157 an adulterant in ground beef 13

Foodborne Disease Outbreak Surveillance System FDOSS Captures outbreak data on agents, foods, and settings responsible for illness Developed: 1967, standardized in 1973 Because: Outbreaks are the major way we learn what foods are causing illness and how to prevent it. Now: States report hundreds of outbreaks each year through the National Outbreak Reporting System (NORS). The data is used to determine pathogen-food combinations to target for prevention. 14

Foodborne Disease Outbreaks, 1973– 2009 1600 ~1, 200 outbreaks/year 1400 1998: improved surveillance 1200 1000 ~500 outbreaks/year Outbreaks 800 600 400 200 0 1973 1978 1983 1988 All data from Foodborne Disease Outbreak Surveillance System. Color of bars indicates improvements in data reporting systems. 1993 1998 2003 2008

Current Hierarchical Scheme for Grouping Foods Into Commodities All Food Represent 17 individual commodities Commodity groups Painter et al, J Food Protection 2009

Source Attribution Definitions Simple foods: foods that Complex foods: foods that can be grouped into only one can be grouped into more than commodity one commodity § ‘Green salad’ with § ‘Lasagna’ with ‘tomatoes, ’ ‘spinach, ’ ‘tomatoes, ’ and ‘noodles, ’ ‘egg, ’ and ‘beef’ ‘carrots’ but Vine-stalk, Grainscontaminated ingredient beans, Egg, Beef is ‘spinach’ Leafy Green § ‘Chow Mein with green salad’ Grains-beans, § ‘Steak’ Beef Pork, Vine-Stalk, Leafy § ‘Fruit salad’ Fruits-nuts Greens, Oils-Sugars 17

Attributing Outbreaks to Simple Foods Outbreak surveillance provides data for determining what foods are major causes of illness Outbreaks Attributed to Simple Food Commodities 2003– 2008 (n=1, 570 outbreaks) Data from Foodborne Disease Outbreak Surveillance System

Annual MMWR Reports and Analysis 2008 http: //www. cdc. gov/outbreaknet/surveillance_data. html

The Foodborne Outbreak Online Database (FOOD) 20

Outline • Background and purpose • Where source attribution starts • Painting a clearer picture – 3 steps to foodborne illness source attribution –Limitations of outbreak data –A palette of different data sources • Looking forward 21

3 Steps to Improved Understanding Step 1: Estimate total number of annual US foodborne illnesses caused by each pathogen Step 2: Attribute illnesses to foods Step 3: Determine the top priority pathogens and their food sources

3 Steps to Improved Understanding Step 1: Estimate total number of annual US foodborne illnesses caused by each pathogen Step 2: Attribute illnesses to foods Step 3: Determine the top priority pathogens and their food sources

Step 1: Estimate Number of Foodborne Illness 24

Annual estimate of domestically acquired foodborne illnesses caused by 31 known pathogens § Nearly 48 million illnesses, resulting in ~128, 000 hospitalizations, 3, 000 deaths § 7 pathogens cause 90% of illnesses, hospitalizations, and deaths due to known pathogens § Salmonella, norovirus, Campylobacter, Toxoplasma, E. coli Listeria, and Clostridium perfringens O 157, § Five pathogens account for 88% of hospitalizations caused by known pathogens § Salmonella, norovirus, Campylobacter, Toxoplasma, E. coli O 157 25

3 Steps to Improved Understanding Step 1: Estimate total number of annual US foodborne illnesses caused by each pathogen Step 2: Attribute illnesses to foods Step 3: Determine the top priority pathogens and their food sources

Attribution of foodborne disease outbreaks and illnesses to simple foods Surveillance for Foodborne Disease Outbreaks, United States, 2008) 27 http: //www. cdc. gov/outbreaknet/pdf/2008 MMWR-Table 2. pdf

3 Steps to Improved Understanding Step 1: Estimate total number of annual US foodborne illnesses caused by each pathogen Step 2: Attribute illnesses to foods Step 3: Determine the top priority pathogens and their food sources

Attribution of foodborne disease outbreaks and illnesses to simple foods Surveillance for Foodborne Disease Outbreaks, United States, 2008 Food Commodity Outbreaks (Illnesses) Top causes of foodborne illness Fish Dairy Eggs Beef Pork Poultry Fruits- Vine. Nuts Stalk Norovirus 0 0 1 (15) 2 (29) 0 0 18 (261) 0 Salmonella 1 (4) 1 (70) 7 (85) 3 (106) 4 (133) 11 (228) 8 (1401) 3 (1604) E. coli STEC 0 3 (24) 0 12 (283) 0 0 1 (5) 4 (103) Campylobacter 0 10 (118) 0 0 1 (27) 3 (16) 0 0 C. perfringens 0 1 (24) 0 6 (330) 5 (358) 6 (150) 0 0 Listeria 0 1 (8) 0 0 0

Determining Major Food Sources Using data from outbreaks caused by simple foods to attribute illnesses to commodities paints a picture of the pathogen-food commodity pairs that contribute to foodborne disease

Outline • Background and purpose • Where source attribution starts • Painting a clearer picture – 3 steps to foodborne illness source attribution –Limitations of outbreak data –A palette of different data sources • Looking forward 31

Limitations of Outbreak Data q q Outbreaks account for a small proportion of total number of foodborne illnesses Need methods that encompass a larger proportion of foodborne illnesses Multi-state Data from Foodborne Diseases Active Surveillance Network (Food. Net) and Foodborne Disease Outbreak Surveillance System

Limitations of Outbreak Data q q More than half of foods reported are complex Many outbreak investigations don’t implicate a single food § Small outbreak § Delay in reporting to public health department q Not all pathogens contributing to foodborne disease cause outbreaks: Toxoplasma gondii

Outline • Background and purpose • Where source attribution starts • Painting a clearer picture – 3 steps to foodborne illness source attribution –Limitations of outbreak data –A palette of different data sources • Looking forward 34

Painting a Clearer Picture The art in the science of source attribution brings in a palette of data sources (colors) and analytic approaches (brushes) to paint a more complete picture of food source attribution Product Testing Data Food Ingredients Consumption Data Surveillance Studies Scientific Experts Surveillance Data Casecontrol Studies Complex Food Attribution Hald Model

Product Testing Data Complex Food Attribution Incorporates food ingredient information to attribute illnesses to both simple and complex foods Food Ingredients Consumption Data Surveillance Studies Data Scientific Experts Surveillance Data Casecontrol Studies Complex Food Attribution Hald Model

The Power of Numbers • In the early 1980’s outbreaks of Salmonella Enteritidis were increasing in the Northeast • Only 7 of 35 (20%) outbreaks specifically implicated eggs • When outbreaks due to egg-containing foods examined, 27 of 35 outbreaks (77%) were associated with eggs Outbreaks in the Northeast Outbreaks in the rest of the country St. Louis et al. JAMA 1988

Estimating the Number of Illnesses Attributed to Each Food Commodity CDC has developed a method to use data from both simple and complex food outbreaks to estimate how many illnesses can be attributed to each food commodity Painter et al. submitted

Studies of sporadic (non-outbreak) cases In case-control studies, people with laboratoryconfirmed infection and healthy “controls” answer questions about exposures Exposures that cause infection are more common among cases Product Testing Data Food Ingredients Consumption Data Surveillance Studies Scientific Experts Surveillance Data Casecontrol Studies Complex Food Attribution Hald Model

Case-control Studies Sources of illness are usually not known § Ill people are not routinely interviewed unless part of an outbreak or a special study , such as a case-control study § People who are sick cannot determine what food (or other exposure) made them sick, and interviewer can’t either • Exposure to contaminated source often days, even weeks, before illness • Case-control studies ask about many exposures, compare exposures of ill persons and non ill persons to identify likely sources, but do not identify the source of an individual illness

Case-control Studies Case-control studies provide population attributable fractions for significant exposures q Source attribution example from studies of Campylobacter infection: q Ø Ø Ø Travel (12% of cases) Chicken (24%) or other meat (21%) consumed in a restaurant Undercooked or pink chicken (3%)

Hald Model A model first published by Danish scientists links food contamination and consumption patterns to foodborne illnesses Product Testing Data Food Ingredients Consumption Data Consumption Surveillance Data Studies Scientific Experts Surveillance Data Casecontrol Studies Complex Food Attribution Hald Model

Hald Model Estimate the expected number of human illnesses attributable to specific food products using human illness data, food consumption data, and pathogen isolation data from food products 43

Adaptation of Hald Attribution Model to US Data • Data Sources • • • US Department of Agriculture (USDA) Food Safety Inspection Service (FSIS) verification testing data Data from CDC on laboratory-confirmed Salmonella infections USDA Economic Research Service data on market availability of food commodities regulated by USDA Guo et al. Foodborne Path Dis. 2011 (http: //www. liebertonline. com/doi/pdfplus/10. 1089/fpd. 2010. 0714)

Painting a Clearer Picture Food borne illness source attribution as determined from outbreak investigations provides the framework for determining the foodpathogen pairs that contribute to foodborne disease However, source attribution can be strengthened by using additional data sources and analytic methods Product Testing Data Food Ingredients Consumption Data Surveillance Studies Scientific Experts Surveillance Data Casecontrol Studies Complex Food Attribution Hald Model

Outline • Background and purpose • Where source attribution starts • Painting a clearer picture • Looking forward 46

Challenge: Communicating Clearly • How to explain uncertainty associated with different estimates • How to interpret “change” – Changing data – Different methods – Real change • What it means to consumers for a food to be “risky”: how to provide information that helps consumers without generating fear 47

Looking Forward q Attribution estimates are always changing: • Data is improving • New data sources are being incorporated • Analytic methods continue to evolve Our goal is to continue to improve estimates by using the best available data and methods, which will enable us to use the most current, accurate, state-of-the-art information when making decisions. 48

Questions?

Thank You! For more information please contact Centers for Disease Control and Prevention 1600 Clifton Road NE, Atlanta, GA 30333 Telephone, 1 -800 -CDC-INFO (232 -4636)/TTY: 1 -888 -232 -6348 E-mail: cdcinfo@cdc. gov Web: www. cdc. gov The 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. National Center for Emerging and Zoonotic Infectious Diseases Enteric Diseases Epidemiology Branch