1 M I C R O B I O L O G I C A L R I S K A S S E S S M E N T S E R I E S 18 Enterohaemorrhagic Escherichia coli in raw beef and beef products: approaches for the provision of scientific advice MEETING REPORT ISSN
2 M I C R O B I O L O G I C A L R I S K A S S E S S M E N T S E R I E S 18 Enterohaemorrhagic Escherichia coli in raw beef and beef products: approaches for the provision of scientific advice MEETING REPORT WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS 2011
3 The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations or of the World Health Organization concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO or WHO in preference to others of a similar nature that are not mentioned. All reasonable precautions have been taken by the World Health Organization and the Food and Agriculture Organization of the United Nations to verify the information contained in this publication. However, the published material is being distributed without warranty of any kind, either expressed or implied. The responsibility for the interpretation and use of the material lies with the reader. In no event shall the World Health Organization and the Food and Agriculture Organization of the United Nations be liable for damages arising from its use. This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of FAO or of WHO. WHO Library Cataloguing-in-Publication Data 1.Escherichia coli infections. 2.Meat products - microbiology. 3.Food poisoning - prevention and control. 4.Food contamination. 5.Risk assessment. I.World Health Organization. II.Food and Agriculture Organization of the United Nations. III.Series. ISBN (NLM classification: WC 290) ISBN ISSN Recommended citation FAO/WHO [Food and Agriculture Organization of the United Nations/World Health Organization] Enterohaemorrhagic Escherichia coli in raw beef and beef products: approaches for the provision of scientific advice: meeting report. Microbiological Risk Assessment Series No. 18. Geneva. 126 pp. All rights reserved. Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders. Requests for permission to reproduce or translate WHO publications should be addressed to WHO Press through the WHO web site (http://www.who.int/about/licensing/copyright_form/en/index.html). FAO and WHO 2011
4 iii Foreword The Members of the Food and Agriculture Organization of the United Nations (FAO) and of the World Health Organization (WHO) have expressed concern regarding the level of safety of food at both national and international levels. Increasing foodborne disease incidence over the last decades seems, in many countries, to be related to an increase in disease caused by microorganisms in food. This concern has been voiced in meetings of the Governing Bodies of both Organizations, and in the Codex Alimentarius Commission. It is not easy to decide whether the suggested increase is real or an artefact of changes in other areas, such as improved disease surveillance or better detection methods for microorganisms in foods. However, the important issue is whether new tools or revised and improved actions can contribute to our ability to lower the disease burden and provide safer food. Fortunately new tools that can facilitate actions seem to be on their way. Over the past decade, Risk Analysis a process consisting of risk assessment, risk management and risk communication has emerged as a structured model for improving our food control systems, with the objectives of producing safer food, reducing the numbers of foodborne illnesses and facilitating domestic and international trade in food. Furthermore, we are moving towards a more holistic approach to food safety, where the entire food chain needs to be considered in efforts to produce safer food. As with any model, tools are needed for the implementation of the risk analysis paradigm. Risk assessment is the science-based component of risk analysis. Science today provides us with in-depth information on life in the world we live in. It has allowed us to accumulate a wealth of knowledge on microscopic organisms, their growth, survival and death, even their genetic make-up. It has given us an understanding of food production, processing and preservation, and of the link between the microscopic and the macroscopic world and how we can benefit from as well as suffer from these microorganisms. Risk assessment provides us with a framework for organizing all this data and information and to better understand the interaction between microorganisms, foods and human illness. It provides us with the ability to estimate the risk to human health from specific microorganisms in foods and gives us a tool with which we can compare and evaluate different scenarios, as well as to identify the types of data necessary for estimating and optimizing mitigating interventions. Microbiological risk assessment can be considered as a tool that can be used in the management of the risks posed by foodborne pathogens and in the elaboration of standards for food in international trade. However, undertaking a microbiological risk assessment (MRA), particularly quantitative MRA, is recognized as a resource-intensive task requiring a multidisciplinary approach. Yet foodborne illness is among the most widespread public health problems, creating social and economic burdens as well as human suffering, making it a concern that all countries need to address. As risk assessment can also be used to justify the introduction of more stringent standards for imported foods, a knowledge of MRA is important for trade purposes, and there is a need to provide countries with the tools for understanding and, if possible, undertaking MRA. This need, combined with that of the Codex Alimentarius for risk-based scientific advice, led FAO and WHO to undertake a programme of activities on MRA at the international level. The Nutrition and Consumer Protection Division, FAO, and the Department of Food Safety and Zoonoses, WHO, are the lead units responsible for this initiative. The two groups have worked together to develop the
5 iv area of MRA at the international level for application at both the national and international levels. This work has been greatly facilitated by the contribution of people from around the world with expertise in microbiology, mathematical modelling, epidemiology and food technology, to name but a few. This Microbiological Risk Assessment series provides a range of data and information to those who need to understand or undertake MRA. It comprises risk assessments of particular pathogen-commodity combinations, interpretative summaries of the risk assessments, guidelines for undertaking and using risk assessment, and reports addressing other pertinent aspects of MRA. We hope that this series will provide a greater insight into MRA, how it is undertaken and how it can be used. We strongly believe that this is an area that should be developed in the international sphere, and have already from the present work clear indications that an international approach and early agreement in this area will strengthen the future potential for use of this tool in all parts of the world, as well as in international standard setting. We would welcome comments and feedback on any of the documents within this series so that we can endeavour to provide Member countries, Codex Alimentarius and other users of this material with the information they need to use risk-based tools, with the ultimate objective of ensuring that safe food is available for all consumers. Mr Samuel C. Jutzi Officer-in-Charge Nutrition and Consumer Protection Division Food and Agriculture Organization of the United Nations Dr M. Maged Younes Director Department of Food Safety and Zoonoses World Health Organization
6 v Contents Contributors (Meeting participants) Experts Resource person Declarations of interest Acknowledgements Abbreviations ix ix ix ix x xi 1. Introduction Background Objectives Scope Hazards of concern EHEC Food commodities of concern 4 2. Review of the risk assessments undertaken to date and their application Introduction Overview of the risk assessments Quantitative risk assessment for Escherichia coli O157:H7 in ground beef hamburgers (Cassin et al., 1998) Shiga toxin-producing E. coli in Ground Beef manufactured from Australian Beef: Process Improvement Draft risk assessment of the public health impact of Escherichia coli O157 in ground beef (USDA-FSIS, 2001) Risk assessment of Shiga-toxin producing Escherichia coli O157 in steak tartare in the Netherlands (Nauta et al., 2001) E. coli O157:H7 in beef burgers produced in the Republic of Ireland: A quantitative microbial risk assessment (Teagasc, 2006) Common features and lessons learned Key management issues associated with EHEC in raw and ready-to-eat beef products Introduction Issues for consideration at pre-harvest stage Issues for consideration at harvest stage (transport, lairage, slaughter and dressing) Issues for consideration at post-harvest stage Other relevant issues Mechanically tenderized meat Intrinsically high risk products (risk communication) 22
7 vi Validation, monitoring and verification, and establishment of equivalence Hazard characterization (including dose-response) Designing approaches for the provision of scientific advice Introduction Flexibility in approach to provision of advice to risk managers Asking risk management questions Application of risk assessment Future application of existing risk assessments Pre-harvest (Live animal) Harvest (transport, lairage, slaughter and dressing) Post-harvest (processing, transport, storage, distribution, preparation, consumption) Assessment of equivalence Dose response Data gaps and future research needs Other information gaps Non-O157 EHECs Dose response Emerging issues Conclusions and recommendations References 39 Annex 1 Background paper 1 Overview of existing risk assessments on enterohaemorrhagic Escherichia coli in meat and meat products 42 A1. Introduction 43 A1.1. EHEC dose-response analyses 43 A1.1.1 Cassin et al., A1.1.2 Lammerding et al., A1.1.3 USDA-FSIS A1.1.4 Nauta et al., A1.1.5 Duffy et al., A1.1.6 Strachan et al., A1.2. Other modelling issues 51 A1.2.1 Addressing uncertainty and variability 51 A1.2.2 Detecting differences 53 A1.2.3 Thorough documentation 54 A1.2.4 Evidence vs intuition 54 A1.3. References 56 Appendix to Annex 1 58
8 vii Annex 2 Background paper 2 An overview of Escherichia coli O157 along the meat chain 60 A2.1. Introduction 60 A2.2. Hazard identification 61 A2.2.1 Characteristics of Escherichia coli O A Genus Escherichia and enterohaemorrhagic E. coli 61 A Definitions associated with E. coli O A Other (i.e. non-o157) serotypes of E. coli that can cause human foodborne illness 63 A2.2.2 Overview of E. coli O157 infections 64 A Incidence 64 A Routes of infection 66 A2.3. Hazard characterization 68 A2.3.1 E. coli O157 infections 68 A Basic mechanism of E. coli O157 infection 68 A Manifestations of human infection 69 A Meats associated with E. coli O157 infections 70 A2.3.2 Dose-response relationship 72 A Infectious dose concept 72 A Probability of infection concept 72 A Factors affecting dose-response 72 A2.4. Exposure assessment 77 A2.4.1 Introduction 77 A2.4.2 E. coli O157 along the meat chain Prevalence and incidence data 77 A Pre-harvest phase 77 A Harvest phase 81 A Post-harvest phase 86 A2.4.3 E. coli O157 along the meat chain Concentration data 89 A2.4.4 Microbial ecology of E. coli O157 in meats 89 A2.4.5 Global trends in meat production and consumption 91 A Trends in meat production 91 A Trends in meat consumption 93
9 viii A2.5. Knowledge gaps and improvements needed 94 A2.5.1 Hazard identification 94 A2.5.2 Hazard characterization 94 A2.5.3 Exposure assessment 95 A Pre-harvest 95 A Harvest 95 A Post-harvest 96 A2.6. References 97 Annex 3 Summary of existing risk assessments 117 A3.1. Quantitative risk assessment for Escherichia coli O157:H7 in ground beef hamburgers (Cassin et al., 1998). 117 A3.2. Shiga toxin-producing E. coli in Ground Beef manufactured from Australian Beef: Process Improvement. 118 A3.3. Draft risk assessment of the public health impact of Escherichia coli O157 in ground beef (USDA-FSIS, 2001) 118 A3.4. Risk assessment of Shiga-toxin producing Escherichia coli O157 in steak tartare in the Netherlands (Nauta et al, 2001). 121 A3.5. E. coli O157:H7 in beef burgers produced in the Republic of Ireland: A quantitative microbial risk assessment (Teagasc, 2006). 124 A3.6. Summary 125 A3.7. References 126
10 ix Contributors (Meeting participants) Experts Wayne Anderson Jeppe Boel Sava Buncic Francis Butler John Cowden Geraldine Duffy Dan Englejohn Teresa Estrada Seamus Fanning Aamir Fazil Ian Jenson Micheál O'Mahony Mark Powell Emma Snary Resource person Alan Reilly Food Safety Authority of Ireland, Ireland Danish Institute for Food and Veterinary Research, Denmark University of Novi Sad, Serbia University College Dublin, Ireland Health Protection Scotland, United Kingdom Teagasc, Ashtown Food Research Centre, Ireland United States Department of Agriculture Food Safety and Inspection Service, United States of America Cinvestat, Mexico University College Dublin, Ireland Public Health Agency of Canada, Canada Meat & Livestock Australia, Australia Food Safety Authority of Ireland, Ireland United States Department of Agriculture Office of Risk Assessment and Cost-Benefit Analysis, United States of America Veterinary Laboratories Agency, United Kingdom Food Safety Authority of Ireland, Ireland Declarations of interest All participants completed a Declaration of Interest form in advance of the meeting. None were considered to present any potential conflict of interest.
11 x Acknowledgements The Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) would like to express their appreciation to all those who contributed to the preparation of this report through the provision of their time and expertise, data and other relevant information. In particular the work of Sava Buncic and Mark Powell in preparing the background discussion papers for the meeting is acknowledged. The meeting was hosted by the Food Safety Authority of Ireland (FSAI). FAO and WHO would like to extend their appreciation to Alan Reilly, Deputy Chief Executive, and his staff for their extensive support in the implementation of this meeting. The preparatory work and expert meeting convened to prepare this report was coordinated by the Secretariat of the Joint FAO/WHO Expert Meetings on Microbiological Risk Assessment (JEMRA). This included Sarah Cahill and Maria de Lourdes Costarrica in FAO and Peter Karim Ben Embarek and Jenny Bishop in WHO. The work was supported and funded by the FAO Nutrition and Consumer Protection Division and the WHO Department of Food Safety and Zoonoses. Final editing for conformity and preparation for printing was by Thorgeir Lawrence.
12 xi Abbreviations A/E CAC CCFH CDC cfu EHEC FAO FDA FSAI FSIS GHP GMP HACCP HC HUS ICMSF JEMRA MLA MLE PFGE QMRA ST Stx STEC Teagasc TTP USDA VT VTEC WHO attaching and effacing [lesions on the surface of epithelial cells] Codex Alimentarius Commission Codex Committee on Food Hygiene Centers for Disease Control and Prevention [USA] Colony forming units Enterohaemorrhagic Escherichia coli Food and Agriculture Organization of the United Nations Food and Drug Administration [of the United States of America] Food Safety Authority of Ireland Food Safety and Inspection Service [USDA] Good hygiene practice Good manufacturing practice Hazard analysis and critical control points Haemorrhagic colitis Haemolytic uraemic syndrome International Commission on Microbiological Specifications for Foods Joint FAO/WHO Expert Meetings on Microbiological Risk Assessment Meat and Livestock Australia Maximum likelihood estimates Pulsed field gel electrophoresis Quantitative microbiological risk assessment Shiga toxin Shiga toxin Shiga toxin producing E. coli Agriculture and Food Development Authority [of Ireland] Thrombotic thrombocytopaenic pupura United States Department of Agriculture Verocytotoxin or verotoxin Verotoxigenic E. coli World Health Organization
14 E. coli in raw beef and beef products Approaches for the provision of scientific advice 1 1. Introduction 1.1 Background Escherichia coli O157:H7 is a member of the enterohaemorrhagic E. coli (EHEC) group of and was first identified as a human pathogen in 1982 when strains of a previously uncommon serotype, O157:H7, were implicated in two outbreaks of haemorrhagic colitis (HC) in the United States of America (Riley et al., 1983). Since then, outbreaks and sporadic cases of EHEC O157:H7 infection continue to be reported in a number of countries throughout the world. Outbreaks of infections from non-o157 serotypes of E. coli, including O26:H11, O103:H2, O104:H21, O111:H8 and O113:H21, are also regularly reported. The symptoms of infection from this group of organisms include bloody diarrhoea and severe abdominal pain, but range from asymptomatic infection to death, with the incubation period ranging from one to eight days. Infection with EHEC may lead to further complications, most notably haemolytic uraemic syndrome (HUS). HUS is characterized by acute kidney failure and is the leading cause of renal failure in young children. The incidence of EHEC varies by country. In 2004, the number of laboratory-confirmed cases in the European Union (17 member states) and Norway was 1.3 cases per population (EFSA, 2006), while in the same year the incidence in the United States of America was 0.9 cases per people (Vugia et al., 2005). In 2001, the incidence in New Zealand was reported to be 2 cases per (Sneyd et al., 2002) and 0.2 cases per in Australia (OzFoodNet, 2001). The frequency of EHEC, and more specifically HUS, appears to be the highest in Argentina, with estimates of approximately 22 cases of HUS per children aged 6 to 48 months (Lopez et al., 1997). While EHEC infections have also been reported for other parts of the world, including a number of African countries, specific incidence data are not always collected or readily available. EHEC infection and associated diseases can occur in any age group; however, it seems that illness occurs most often in young children. For example, in Japan, the median age for EHEC illness has been reported to be 8 years (Kawamura, Yamazaki and Tamai, 1999). Children less than five years of age appear to be the most susceptible to HUS, while EHEC infections in the elderly lead more often to thrombotic thrombocytopaenic pupura (TTP) (Banatvala et al., 2001). EHECs have been isolated from various domestic animals and wildlife, including cattle, sheep, swine, goats and deer. Ruminants, and in particular cattle, are considered a major reservoir of EHEC. While multiple sources and routes of transmission are now recognized, data based on outbreaks and sporadic infections indicate beef and beef products as the most frequently identified source of foodborne EHEC infection. In particular, undercooked ground beef products have emerged as an important source of foodborne infection. Other foodborne sources include milk and dairy products (e.g. unpasteurized milk, cheese from raw milk), fresh produce (e.g. sprouts, salads), drinks (e.g. apple cider or juice) and water. Dozens of new outbreaks have been reported implicating different sources and illustrating the multifaceted epidemiology of EHEC infections. The Codex Committee on Food Hygiene (CCFH) is considering addressing the need for risk-based control of EHEC. A risk profile has been prepared as the basis for further work in this area (CCFH, 2005). The Committee has noted that no international risk assessment has
15 2 Meeting Report been undertaken on this issue and suggested that this could be the next step in order to move forward (CAC, 2004). Taking into consideration the ongoing public health problem of EHEC in their member countries, the impact of this pathogen on meat trade, and the suggestion from Codex to undertake a risk assessment on this issue, FAO and WHO consider that this highlights the need for urgent attention at both national and international level to develop appropriate management interventions. Therefore, as part of JEMRA activities, FAO and WHO, together with the Food Safety Authority of Ireland (FSAI), convened an inception meeting on enterohaemorrhagic E. coli in raw meat and meat products from 4 7 September 2006 in Dublin, Ireland. This meeting was convened to provide guidance to FAO and WHO on the appropriate steps in the development of this activity before embarking on any risk assessment work. As well as providing guidance to FAO and WHO in their future work on EHEC, the outcome of the meeting will be made available to CCFH to assist the committee in its efforts to develop risk management guidance documents on EHEC and to facilitate its interaction with FAO and WHO on defining and clarifying the scientific advice needed for this work. To assist the participants in their deliberations, FAO and WHO commissioned the preparation of two background papers: one provided an update on the current state of knowledge on the bacteria and related issues at the time of the meeting, while the other gave a description and analysis of the risk assessments that had already been undertaken in a number of Member States. These two documents are appended as Annexes 1 and 2 to this report. 1.2 Objectives It has been noted that a number of risk assessments have already been undertaken on EHEC in meat and meat products and that there is experience in some countries on the risk management of this issue. The meeting was convened to review the current state of knowledge on EHEC in terms of existing risk assessments and related information. In doing so, the meeting was requested to consider the risk management actions, if any, that resulted from those risk assessments and to identify what was useful about the existing risk assessments from a risk management perspective, as well as identifying the strengths and weaknesses of the risk assessments. Based on this review and discussion, a roadmap for future FAO/WHO activities in this area would be developed to inform the process of riskbased management of EHEC in raw beef and beef products in CCFH and in member countries. The specific objectives of the meeting were to: Review the existing risk assessments on EHEC in terms of (a) their fulfilling their scope and providing the basis for scientifically-based risk-management actions; and (b) their potential application (in whole or on a modular basis) to the development of a risk assessment at the international level. Consider the risk management actions, if any, taken to date that were based on risk assessment and identify the strengths and weakness of the risk assessments from a risk management perspective, in particular identifying when and why the risk assessments did not meet the needs of risk managers. Identify the key issues currently faced by risk managers in terms of addressing the problems associated with EHEC in raw beef and beef products.
16 E. coli in raw beef and beef products Approaches for the provision of scientific advice 3 Considering the output of the above objectives and the existing data on EHEC in raw beef and beef products, provide guidance to FAO and WHO on the specific areas to be addressed in any future work on this issue, and how to address them. 1.3 Scope Hazards of concern The hazard of concern that was the focus of this meeting was EHEC. However, throughout this document specific mention is made of one particular EHEC, verotoxin producing E. coli O157:H7, because of its implication in the first recognized outbreak of EHEC infection. In addition, several other major outbreaks, coupled with its unique physiology (in terms of EHEC) have resulted in E. coli O157:H7 being the EHEC most frequently referred to and most extensively described in the literature EHEC Verocytotoxin producing Escherichia coli is a term used to describe strains of E. coli characterized by the ability to produce verocytotoxin(s) (VT), or just verotoxins that are capable of killing vero cells, a tissue culture line of monkey kidney cells. This group, often referred to as verotoxigenic E. coli or VTEC, includes over 100 serogroups in addition to E. coli O157:H7. Furthermore, it is recognized that the terms Shiga toxin producing E. coli (STEC) and VTEC as well as the terms Shiga toxin(s) (ST or Stx) and verocytotoxin or verotoxin (VT) are used interchangeably worldwide. A more extensive description of the relevant terms is provided in Section A2.1 of Annex 2. EHEC is defined as a subgroup of VTEC/STEC associated with human diseases and which in addition to the verocytotoxin/shigatoxin producing capacity harbours additional genes that are important in virulence. These include the genes encoded in the pathogenicity island designated LEE (locus of enterocyte effacement), which can cause attaching and effacing lesions on the surface of epithelial cells (A/E factor, usually determined by the presence of the intimin (eae gene) and a 60 MDa virulence plasmid (usually determined by the presence of the ehx gene). It should be noted that the clinical outcome of an infection might not necessarily include HC or HUS. In addition to E. coli O157, EHEC includes other serotypes causing foodborne illness, such as O26, O111, O113 and O121. Due to the paucity of information on most other EHECs, the scope of this paper was limited to E. coli O157:H7 or VTEC O157 when discussing strain- or serotype-specific data, on the assumption that this is where most of the data are available. However, assuming that the behaviour of E. coli O157:H7 would be similar to other relevant EHEC serotypes, the advice provided would be applicable for most if not all EHECs. In other words, the strategy recommended on how to control EHEC is based on our knowledge of O157:H7. The meeting nevertheless recognized that such a generalization may not be appropriate as more information on other EHECs becomes available Food commodities of concern It is commonly accepted that the primary reservoirs of EHEC are farm ruminants, and in particular cattle. It is, however, unclear to what extent EHEC can be considered ubiquitous in cattle, and what the reasons are for the sporadic nature of EHEC and the variation in prevalence in cattle in different regions of the world.
17 4 Meeting Report The main recognized routes of EHEC infection are: person-to-person transmission; contact with animals; foodborne transmission; and waterborne transmission. Only the foodborne route is considered further in this document. Food vehicles implicated most frequently in outbreaks of EHEC infection have been raw or undercooked foods of bovine origin, especially undercooked ground beef and unpasteurized milk (CCFH, 2005). A number of case-control studies have identified ground beef as an important risk factor for EHEC infection, with current data based on outbreaks and sporadic infections indicating that consumption of ground beef remains the single most frequently identified source of foodborne EHEC infection. Dry fermented meats, as well as cooked and fermented sausages, have also been implicated in reported outbreaks of EHEC infection. However, an increasing number of outbreaks have been associated with the consumption of raw or minimally processed fruits and vegetables. Leafy green vegetables, such as lettuce, have been implicated in a number of large outbreaks of E. coli O157:H7, some of which had serious public health impacts (Hilborn, Mermin and Mshar, 1999; Martin et al., 1986; US FDA, 2006, 2007). These are an important source of human cases of foodborne illness due to EHEC as they are subject to contamination and eaten raw (CAC, 2002). Thus, while recognizing the importance of other sources of foodborne EHEC infections, the meeting decided to restrict the scope of its work to raw ground beef and beef products along the entire food chain from primary production to consumption. This restriction was also motivated by the availability of data. Figure 1 illustrates the routes of transmission and products of concern considered during the meeting.
18 E. coli in raw beef and beef products Approaches for the provision of scientific advice 5 Human Reservoir Environmental Reservoir Animal Reservoir Cattle Other animals sheep, pigs, pets, etc. Milk and dairy products Beef and beef Products Non-animal products Pre-harvest (on-farm activities) Harvest (transport, lairage, slaughter, dressing) Pathway outside the scope of the meeting Post-harvest (boning, processing, distribution, retail, preparation, consumption) Pathway within the scope of the meeting Primal cuts e.g. beef joints Ready-to-eat processed beef products e.g. fermented beef products Raw processed beef products e.g. ground beef, mechanically tenderized beef Figure 1. Routes of transmission of EHEC and products of concern considered during the meeting.