Characteristics of foodborne disease outbreak investigations conducted by Foodborne Diseases Active Surveillance Network (FoodNet) sites, 2003-2008

Barriers to stool specimen collection during foodborne and enteric illness outbreak investigations in Arizona and Colorado

Stool specimen collection during a foodborne or enteric illness outbreak investigation is essential for determining the outbreak etiology and for advancing the epidemiologic understanding of the pathogens and food vehicles causing illness. However, public health professionals face multifaceted barriers when trying to collect stool specimens from ill person during an outbreak investigation. The Colorado Integrated Food Safety Center of Excellence (Colorado IFS CoE) and the Arizona Department of Health Services surveyed local public health agencies (LPHAs) to identify barriers to collecting ≥2 clinical specimens in foodborne and enteric illness outbreaks. The most commonly selected patient-related barrier was that the patient did not think it is important to provide a stool sample because they are well by the time the LPHA follows-up (61%). The most frequently selected outbreak-related barrier was the LPHA did not learn about the outbreak until after symptoms had resolved (61%). Time/personnel not being available for stool collection was the most frequently chosen health department-related barrier (51%). Timing of the outbreak (e.g., on a weekend or holiday) was the most frequently selected transportation-related barrier (51%) to collecting ≥2 stool specimens. Many of the frequently cited barriers in this survey were similar to those previously reported, such as workforce capacity and patient privacy concerns, indicating that these barriers are ongoing. Reducing barriers to stool collection during outbreaks will require efforts led at the national and state levels, such as increased enteric illness program funding, educating public health staff on the importance of specimen collection during every enteric illness outbreak, and providing specimen collection resources to LPHA staff.

Foodborne Illness Outbreaks Reported to National Surveillance, United States, 2009–2018

Foodborne outbreaks reported to national surveillance systems represent a subset of all outbreaks in the United States; not all outbreaks are detected, investigated, and reported. We described the structural factors and outbreak characteristics of outbreaks reported during 2009–2018. We categorized states (plus DC) as high (highest quintile), middle (middle 3 quintiles), or low (lowest quintile) reporters on the basis of the number of reported outbreaks per 10 million population. Analysis revealed considerable variation across states in the number and types of foodborne outbreaks reported. High-reporting states reported 4 times more outbreaks than low reporters. Low reporters were more likely than high reporters to report larger outbreaks and less likely to implicate a setting or food vehicle; however, we did not observe a significant difference in the types of food vehicles identified. Per capita funding was strongly associated with increased reporting. Investments in public health programming have a measurable effect on outbreak reporting.

High-Efficiency Machine Learning Method for Identifying Foodborne Disease Outbreaks and Confounding Factors

The China National Center for Food Safety Risk Assessment (CFSA) uses the Foodborne Disease Monitoring and Reporting System (FDMRS) to monitor outbreaks of foodborne diseases across the country. However, there are problems of underreporting or erroneous reporting in FDMRS, which significantly increase the cost of related epidemic investigations. To solve this problem, we designed a model to identify suspected outbreaks from the data generated by the FDMRS of CFSA. In this study, machine learning models were used to fit the data. The recall rate and F1-score were used as evaluation metrics to compare the classification performance of each model. Feature importance and pathogenic factors were identified and analyzed using tree-based and gradient boosting models. Three real foodborne disease outbreaks were then used to evaluate the best performing model. Furthermore, the SHapley Additive exPlanation value was used to identify the effect of features. Among all machine learning classification models, the eXtreme Gradient Boosting (XGBoost) model achieved the best performance, with the highest recall rate and F1-score of 0.9699 and 0.9582, respectively. In terms of model validation, the model provides a correct judgment of real outbreaks. In the feature importance analysis with the XGBoost model, the health status of the other people with the same exposure has the highest weight, reaching 0.65. The machine learning model built in this study exhibits high accuracy in recognizing foodborne disease outbreaks, thus reducing the manual burden for medical staff. The model helped us identify the confounding factors of foodborne disease outbreaks. Attention should be paid not only to the health status of those with the same exposure but also to the similarity of the cases in time and space.

Methods for generating hypotheses in human enteric illness outbreak investigations: a scoping review of the evidence

Enteric illness outbreaks are complex events, therefore, outbreak investigators use many different hypothesis generation methods depending on the situation. This scoping review was conducted to describe methods used to generate a hypothesis during enteric illness outbreak investigations. The search included five databases and grey literature for articles published between 1 January 2000 and 2 May 2015. Relevance screening and article characterisation were conducted by two independent reviewers using pretested forms. There were 903 outbreaks that described hypothesis generation methods and 33 papers which focused on the evaluation of hypothesis generation methods. Common hypothesis generation methods described are analytic studies (64.8%), descriptive epidemiology (33.7%), food or environmental sampling (32.8%) and facility inspections (27.9%). The least common methods included the use of a single interviewer (0.4%) and investigation of outliers (0.4%). Most studies reported using two or more methods to generate hypotheses (81.2%), with 29.2% of studies reporting using four or more. The use of multiple different hypothesis generation methods both within and between outbreaks highlights the complexity of enteric illness outbreak investigations. Future research should examine the effectiveness of each method and the contexts for which each is most effective in efficiently leading to source identification.

Food-Associated Stress Primes Foodborne Pathogens for the Gastrointestinal Phase of Infection

The incidence of foodborne outbreaks and product recalls is on the rise. The ability of the pathogen to adapt and survive under stressful environments of food processing and the host gastrointestinal tract may contribute to increasing foodborne illnesses. In the host, multiple factors such as bacteriolytic enzymes, acidic pH, bile, resident microflora, antimicrobial peptides, and innate and adaptive immune responses are essential in eliminating pathogens. Likewise, food processing and preservation techniques are employed to eliminate or reduce human pathogens load in food. However, sub-lethal processing or preservation treatments may evoke bacterial coping mechanisms that alter gene expression, specifically and broadly, resulting in resistance to the bactericidal insults. Furthermore, environmentally cued changes in gene expression can lead to changes in bacterial adhesion, colonization, invasion, and toxin production that contribute to pathogen virulence. The shared microenvironment between the food preservation techniques and the host gastrointestinal tract drives microbes to adapt to the stressful environment, resulting in enhanced virulence and infectivity during a foodborne illness episode.

Comparing Characteristics of Sporadic and Outbreak-Associated Foodborne Illnesses, United States, 2004-2011

Our findings do not warrant rejecting the hypothesis that outbreak and sporadic illnesses are similar.

Comparing Sporadic and Outbreak Foodborne Illness

Outbreak data have been used to estimate the proportion of illnesses attributable to different foods. Applying outbreak-based attribution estimates to nonoutbreak foodborne illnesses requires an assumption of similar exposure pathways for outbreak and sporadic illnesses. This assumption cannot be tested, but other comparisons can assess its veracity. Our study compares demographic, clinical, temporal, and geographic characteristics of outbreak and sporadic illnesses from Campylobacter, Escherichia coli O157, Listeria, and Salmonella bacteria ascertained by the Foodborne Diseases Active Surveillance Network (FoodNet). Differences among FoodNet sites in outbreak and sporadic illnesses might reflect differences in surveillance practices. For Campylobacter, Listeria, and Escherichia coli O157, outbreak and sporadic illnesses are similar for severity, sex, and age. For Salmonella, outbreak and sporadic illnesses are similar for severity and sex. Nevertheless, the percentage of outbreak illnesses in the youngest age category was lower. Therefore, we do not reject the assumption that outbreak and sporadic illnesses are similar.

2017 Infectious Diseases Society of America Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea

These guidelines are intended for use by healthcare professionals who care for children and adults with suspected or confirmed infectious diarrhea. They are not intended to replace physician judgement regarding specific patients or clinical or public health situations. This document does not provide detailed recommendations on infection prevention and control aspects related to infectious diarrhea.

Characteristics of foodborne outbreaks in which use of analytical epidemiological studies contributed to identification of suspected vehicles, European Union, 2007 to 2011

Foodborne disease outbreaks (FBDOs) occur frequently in Europe. Employing analytical epidemiological study designs increases the likelihood of identifying the suspected vehicle(s), but these studies are rarely applied in FBDO investigations. We used multivariable binary logistic regression analysis to identify characteristics of investigated FBDOs reported to the European Food Safety Authority (2007-2011) that were associated with analytical epidemiological evidence (compared to evidence from microbiological investigations/descriptive epidemiology only). The analysis was restricted to FBDO investigations, where the evidence for the suspected vehicle was considered 'strong', i.e. convincing. The presence of analytical epidemiological evidence was reported in 2012 (50%) of these 4038 outbreaks. In multivariable analysis, increasing outbreak size, number of hospitalizations, causative (i.e. aetiological) agent (whether identified and, if so, which one), and the setting in which these outbreaks occurred (e.g. geographically dispersed outbreaks) were independently associated with presence of analytical evidence. The number of investigations with reported analytical epidemiological evidence was unexpectedly high, likely indicating the need for quality assurance within the European Union foodborne outbreak reporting system, and warranting cautious interpretation of our findings. This first analysis of evidence implicating a food vehicle in FBDOs may help to inform public health authorities on when to use analytical epidemiological study designs.

Poultry: the most common food in outbreaks with known pathogens, United States, 1998–2012

As poultry consumption continues to increase worldwide, and as the United States accounts for about one-third of all poultry exports globally, understanding factors leading to poultry-associated foodborne outbreaks in the United States has important implications for food safety. We analysed outbreaks reported to the United States’ Foodborne Disease Outbreak Surveillance System from 1998 to 2012 in which the implicated food or ingredient could be assigned to one food category. Of 1114 outbreaks, poultry was associated with 279 (25%), accounting for the highest number of outbreaks, illnesses, and hospitalizations, and the second highest number of deaths. Of the 149 poultry-associated outbreaks caused by a confirmed pathogen, Salmonella enterica (43%) and Clostridium perfringens (26%) were the most common pathogens. Restaurants were the most commonly reported location of food preparation (37% of poultry-associated outbreaks), followed by private homes (25%), and catering facilities (13%). The most commonly reported factors contributing to poultry-associated outbreaks were food-handling errors (64%) and inadequate cooking (53%). Effective measures to reduce poultry contamination, promote safe food-handling practices, and ensure food handlers do not work while ill could reduce poultry-associated outbreaks and illnesses.

Foodborne Outbreaks Reported to the U.S. Food Safety and Inspection Service, Fiscal Years 2007 through 2012

The U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) works closely with federal, state, and local public health partners to investigate foodborne illness outbreaks associated with its regulated products. To provide insight into outbreaks associated with meat and poultry, outbreaks reported to FSIS during fiscal years 2007 through 2012 were evaluated. Outbreaks were classified according to the strength of evidence linking them to an FSIS-regulated product and by their epidemiological, etiological, and vehicle characteristics. Differences in outbreak characteristics between the period 2007 through 2009 and the period 2010 through 2012 were assessed using a chi-square test or Mann-Whitney U test. Of the 163 reported outbreaks eligible for analysis, 89 (55%) were identified as possibly linked to FSIS-regulated products and 74 (45%) were definitively linked to FSIS-regulated products. Overall, these outbreaks were associated with 4,132 illnesses, 772 hospitalizations, and 19 deaths. Shiga toxin-producing Escherichia coli was associated with the greatest proportion of reported outbreaks (55%), followed by Salmonella enterica (34%) and Listeria monocytogenes (7%). Meat and poultry products commercially sold as raw were linked to 125 (77%) outbreaks, and of these, 105 (80%) involved beef. Over the study period, the number of reported outbreaks definitively linked to FSIS-regulated products (P = 0.03) declined, while the proportion of culture-confirmed cases (P = 0.0001) increased. Our findings provide insight into the characteristics of outbreaks associated with meat and poultry products.

The rise and decline inSalmonella entericaserovar Enteritidis outbreaks attributed to egg-containing foods in the United States, 1973–2009

Salmonella entericacauses an estimated 1 million domestically acquired foodborne illnesses annually.Salmonella entericaserovar Enteritidis (SE) is among the top three serovars of reported cases ofSalmonella. We examined trends in SE foodborne outbreaks from 1973 to 2009 using Joinpoint and Poisson regression. The annual number of SE outbreaks increased sharply in the 1970s and 1980s but declined significantly after 1990. Over the study period, SE outbreaks were most frequently attributed to foods containing eggs. The average rate of SE outbreaks attributed to egg-containing foods reported by states began to decline significantly after 1990, and the proportion of SE outbreaks attributed to egg-containing foods began declining after 1997. Our results suggest that interventions initiated in the 1990s to decrease SE contamination of shell eggs may have been integral to preventing SE outbreaks.

The national web-based outbreak rapid alert system in Norway: eight years of experience, 2006-2013

In 2005, the Norwegian Institute of Public Health established a web-based outbreak rapid alert system called Vesuv. The system is used for mandatory outbreak alerts from municipal medical officers, healthcare institutions, and food safety authorities. As of 2013, 1426 outbreaks have been reported, involving 32913 cases. More than half of the outbreaks occurred in healthcare institutions (759 outbreaks, 53·2%). A total of 474 (33·2%) outbreaks were associated with food or drinking water. The web-based rapid alert system has proved to be a helpful tool by enhancing reporting and enabling rapid and efficient information sharing between different authorities at both the local and national levels. It is also an important tool for event-based reporting, as required by the International Health Regulations (IHR) 2005. Collecting information from all the outbreak alerts and reports in a national database is also useful for analysing trends, such as occurrence of certain microorganisms, places or sources of infection, or route of transmission. This can facilitate the identification of specific areas where more general preventive measures are needed.

Summary of 11 years of enteric outbreak investigations and criteria to initiate an investigation, Province of Quebec, 2002 through 2012

This article presents a retrospective analysis of enteric disease outbreak investigations led by or conducted in collaboration with provincial health authorities in the Province of Quebec from 2002 through 2012. Objectives were to characterize enteric disease outbreaks, quantify and describe those for which a source was identified (including the control measures implemented), identify factors that contributed to or impeded identification of the source, and recommend areas for improvement in outbreak investigations (including establishment of criteria to initiate investigations). A descriptive analysis of enteric disease outbreak summaries recorded in a provincial database since 2002 was conducted, and corresponding outbreak reports were reviewed. Among 61 enteric disease outbreaks investigated, primary pathogens involved were Salmonella (46%), Escherichia coli O157:H7 (25%), and Listeria monocytogenes (13%). Sources were identified for 37 (61%) of 61 of the outbreaks, and descriptive studies were sufficient to identify the source for 26 (70%) of these. During the descriptive phase of the investigation, the causes of 21 (81%) of 26 outbreaks were identified by promptly collecting samples of suspected foods based on case interviews. Causes of outbreaks were more likely to be detected by weekly surveillance or alert systems (odds ratio = 6.0, P = 0.04) than by serotyping or molecular typing surveillance and were more likely to be associated with a common event or location (odds ratio = 11.0, P = 0.023). Among the 37 outbreaks for which causes were identified, 24 (65%) were associated with contaminated food, and recalls were the primary control measure implemented (54%). Review of enteric outbreaks investigated at the provincial level in Québec has increased the province's ability to quantify success and identify factors that can promote success. Multiple criteria should be taken into account to identify case clusters that are more likely to be resolved.

Creating student sleuths: how a team of graduate students helped solve an outbreak of Salmonella Heidelberg infections associated with kosher broiled chicken livers

Since 2009, the New York City Department of Health and Mental Hygiene (DOHMH) has received FoodCORE funding to hire graduate students to conduct in-depth food exposure interviews of salmonellosis case patients. In 2011, an increase in the number of Salmonella Heidelberg infections with pulsed-field gel electrophoresis Xba I pattern JF6X01.0022 among observant Jewish communities in New York and New Jersey was investigated. As this pattern is common nationwide, some cases identified were not associated with the outbreak. To reduce the number of background cases, DOHMH focused on the community initially identified in the outbreak and defined a case as a person infected with the outbreak strain of Salmonella Heidelberg with illness onset from 1 April to 17 November 2011 and who consumed a kosher diet, spoke Yiddish, or self-identified as Jewish. Nationally, 190 individuals were infected with the outbreak strain of Salmonella Heidelberg; 63 New York City residents met the DOHMH case definition. In October 2011, the graduate students (Team Salmonella) interviewed three case patients who reported eating broiled chicken livers. Laboratory testing of chicken liver samples revealed the outbreak strain of Salmonella Heidelberg. Although they were only partially cooked, the livers appeared fully cooked, and consumers and retail establishment food handlers did not cook them thoroughly before eating or using them in a ready-to-eat spread. This investigation highlighted the need to prevent further illnesses from partially cooked chicken products. Removing background cases helped to focus the investigation. Training graduate students to collect exposure information can be a highly effective model for conducting foodborne disease surveillance and outbreak investigations for local and state departments of public health.

Improving Response to Foodborne Disease Outbreaks in the United States: Findings of the Foodborne Disease Centers for Outbreak Response Enhancement (FoodCORE), 2010-2012

CONTEXT

Each year foodborne diseases (FBD) affect approximately 1 in 6 Americans, resulting in 128 000 hospitalizations and 3000 deaths. Decreasing resources impact the ability of public health officials to identify, respond to, and control FBD outbreaks. Geographically dispersed outbreaks necessitate multijurisdictional coordination across all levels of the public health system. Rapid response depends on rapid detection.

OBJECTIVE

Targeted resources were provided to state and local health departments to improve completeness and timeliness of laboratory, epidemiology, and environmental health (EH) activities for FBD surveillance and outbreak response.

DESIGN

Foodborne Disease Centers for Outbreak Response Enhancement (FoodCORE) centers, selected through competitive award, implemented work plans designed to make outbreak response more complete and faster in their jurisdiction. Performance metrics were developed and used to evaluate the impact and effectiveness of activities.

PARTICIPANTS

Departments of Health in Connecticut, New York City, Ohio, South Carolina, Tennessee, Utah, and Wisconsin.

RESULTS

From the first year (Y1) of the program in October 2010 to the end of the second year (Y2) in December 2012, the centers completed molecular subtyping for a higher proportion of Salmonella, Shiga toxin-producing Escherichia coli, and Listeria (SSL) isolates (86% vs 98%) and reduced the average time to complete testing from a median of 8 to 4 days. The centers attempted epidemiologic interviews with more SSL case-patients (93% vs 99%), and the average time to attempt interviews was reduced from a median of 4 to 2 days. During Y2, nearly 200 EH assessments were conducted. FoodCORE centers began documenting model practices such as streamlining and standardizing case-patient interviewing.

CONCLUSION

Centers used targeted resources and process evaluation to implement and document practices that improve the completeness and timeliness of FBD surveillance and outbreak response activities in several public health settings. FoodCORE strategies and model practices could be replicated in other jurisdictions to improve FBD response.

Reducing the barriers against analytical epidemiological studies in investigations of local foodborne disease outbreaks in Germany – a starter kit for local health authorities

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How to diagnose a foodborne illness

Timely diagnosis of foodborne infection can be critical not only for the patient, but also for the larger community because of the potential to interrupt further spread. This article presents the diagnostic approach to patients with foodborne illness, discussing epidemiologic clues of various foodborne pathogens and their distinguishing clinical features of diagnostic importance. Also discussed are situations whereby stool cultures should be ordered; other helpful stool tests; nonculture methods of identifying organisms and their applicability in clinical settings; the role of pulsed-field gel electrophoresis in typing organisms; and large-scale sharing of data to aid in identification of large outbreaks.

Attributing sporadic and outbreak-associated infections to sources: blending epidemiological data

Common sources of shiga toxin-producing Escherichia coli (STEC) O157 infection have been identified by investigating outbreaks and by case-control studies of sporadic infections. We conducted an analysis to attribute STEC O157 infections ascertained in 1996 and 1999 by the Foodborne Diseases Active Surveillance Network (FoodNet) to sources. Multivariable models from two case-control studies conducted in FoodNet and outbreak investigations that occurred during the study years were used to calculate the annual number of infections attributable to six sources. Using the results of the outbreak investigations alone, 27% and 15% of infections were attributed to a source in 1996 and 1999, respectively. Combining information from both data sources, 65% of infections in 1996 and 34% of infections in 1999 were attributed. The results suggest that methods to incorporate data from multiple surveillance systems and over several years are needed to improve estimation of the number of illnesses attributable to exposure sources.

Interaction of nutrition and infections globally: an overview

The interaction of nutrition and infections is known by experience by generations of medical doctors. Before the era of antibiotics, diet was an integral part of the management of infections. Now, it is necessary to take a fresh look at this interaction as the understanding of immune response has expanded considerably. Comparatively little research has addressed the impact of nutrition interventions on the management of infectious diseases. Most observations of the interaction between nutrition and infections are epidemiological in character. This holds especially true for measles as well as for tuberculosis. In AIDS, the deterioration of the nutritional status is an indicator of disease progression. Infections in undernourished children are a common cause of death, and taking this finding into account helps to reduce the case fatality rate in severely malnourished patients. Regarding the immune response, cellular as well as soluble components are affected by deficiencies of single nutrients or general undernutrition. The immunosuppressive effect of undernutrition starts during intrauterine life already: maternal nutrition status has been shown to impact on immune function in adult animals. Recent research suggests that not only undernutrition but also caloric overnutrition impacts on immune response to infections and immunization. This is partly due to the chronic inflammatory activity of the adipose tissue and partly due to neuroendocrine alterations. Infectious diseases also impact on the nutritional status, either specifically or through unspecific mechanisms, such as anorexia, tachypnea, and vomiting.

Variability among states in investigating foodborne disease outbreaks

Over 1,100 foodborne disease outbreaks cause over 23,000 illnesses in the United States annually, but the rates of outbreaks reported and successful investigation vary dramatically among states. We used data from the Centers for Disease Control and Prevention's outbreak reporting database, Association of Public Health Laboratories' PulseNet laboratory subtyping network survey and Salmonella laboratory survey, national public health surveillance data, and national surveys to examine potential causes of this variability. The mean rate of reporting of Salmonella outbreaks was higher in states requiring submission of all isolates to the state public health laboratory, compared to those that do not (5.9 vs. 4.1 per 10 million population, p=0.0062). Rates of overall outbreak reporting or successful identification of an etiology or food vehicle did not correlate at the state level with population, rates of sporadic disease reporting, health department organizational structure, or self-reported laboratory or epidemiologic capacity. Foodborne disease outbreak surveillance systems are complex, and improving them will require a multi-faceted approach to identifying and overcoming barriers.