Common Source Outbreak Research Articles

Multi‐country outbreak of Salmonella Agona infections possibly linked to ready‐to‐eat food

A multi-country outbreak of Salmonella Agona (S. Agona) is under investigation in the European Union (EU). Overall, 147 cases were reported by five EU countries: 122 cases since 01/01/2017, and 25 historical cases between 2014 and 2016. The United Kingdom (UK) reported most cases (129), followed by Finland (15), Denmark, Germany and Ireland (one case each). The outbreak was first detected in UK using whole genome sequencing. The close genomic relationship and the distinct seasonal spring peaks suggest that cases are part of an intermittent common source outbreak. Seventeen S. Agona food isolates from 2018, detected in UK, were found to be closely genetically related to the human strains. The contaminated food, sampled in UK, were cucumbers sampled during processing before/after washing and ready-to-eat (RTE) food products containing cucumbers. At present, there is insufficient epidemiological information available on the consumption of contaminated products to support the microbiological evidence provided by the isolation of the outbreak strain in food. Although the cucumbers used in all final contaminated products originated from Spain for a limited period (November/2017-April/2018), no connection between supply chains was identified: primary producers of cucumbers were different, and cucumbers were delivered to different processing companies through different distributors in UK. All cucumber samples, taken either at primary production level in Spain or during distribution to/within UK, were Salmonella negative. The available microbiological evidence suggests RTE products containing cucumbers as a possible vehicle of infection but so far it has not been possible to identify the specific point in the production chain where the contamination occurred. Further investigations are needed to identify the source of contamination. Until the source of infection and the point of contamination along the food production chain have been identified/controlled, new cases may occur, with a high likelihood that the outbreak strains will re-emerge in 2019.

National molecular tracing network for foodborne disease surveillance in China

To improve the early detection of geographically dispersed common-source foodborne outbreaks, a national foodborne disease molecular tracing network (TraNet) was launched in 2013 based on the existing laboratory-based foodborne disease surveillance system in China. TraNet consists of 32 provincial and many municipal Centers for Disease Control and Prevention that conduct molecular subtyping using pulsed-field gel electrophoresis (PFGE) on foodborne pathogens submitted by sentinel hospitals within their jurisdictions, and submit these PFGE profiles to a national database for further analysis. Currently, TraNet plays a significant role in the identification of etiologic causes and tracks contaminated food during foodborne outbreaks.

A Large Common Source Outbreak of Salmonella typhimurium Linked to Kuala Terengganu Night Markets, Malaysia, 2014

On 1 Mar 2014, the Terengganu District Health Office was notified of ten patients presented with acute gastroenteritis at Sultanah Nur Zahirah Hospital. Their illness was linked to consumption of foods from two night markets. An outbreak investigation was initiated to determine the source of the outbreak. Case finding was conducted in the hospital, and community. Patients were interviewed about demographics, symptoms and food consumption history. Stool samples from patients and food handlers as well as food and environmental samples were collected for laboratory analysis. Suspected food premises were inspected. A case-control study was conducted. Of 169 cases, 68.6% and 32.5% ate food from night markets A and B respectively while 1.2% ate food from both night markets. Major symptom was diarrhea (98.2%). There was one death from hypovolemic shock. Salmonella typhimurium was isolated from 13 patients and one food handler. All isolates showed genetic similarity by pulsed-field gel electrophoresis. The food handler tested to have the infection served the white fried rice sold in both night markets. Cases were 14 (95% CI = 4.05-46.61) and nine (95% CI = 3.36-24.3) times more likely to have consumed white fried rice from night markets A & B respectively. The source of infection was likely to be white fried rice that was prepared at the same place, contaminated by an infected food handler and sold at both night markets.

Blastomycosis in Wisconsin: Beyond the Outbreaks.

In the summer of 2015, many individuals visiting the Little Wolf River in Waupaca County were exposed to the pathogenic fungus, Blastomyces. Over time, 59 confirmed and 39 probable cases were reported to the Wisconsin Department of Health Services (W-DHS), making this one of the largest outbreaks in recent state history. Though most instances of blastomycosis are not associated with common source outbreaks, cases such as this highlight the need for vigilance regarding this preventable cause of death. In the state of Wisconsin, an average of 118.6 cases (range, 84-174) of confirmed blastomycosis are diagnosed annually; the majority of these cases are sporadic rather than outbreak-associated. In the current study, we review characteristics of blastomycosis cases diagnosed at our academic medical center, as well as examine statewide W-DHS data, in order to familiarize pathologists with the epidemiologic and histologic characteristics of this disease.

A large common-source outbreak of norovirus gastroenteritis in a hotel in Singapore, 2012.

An outbreak of gastroenteritis affected 453 attendees (attack rate 28·5%) of six separate events held at a hotel in Singapore. Active case detection, case-control studies, hygiene inspections and microbial analysis of food, environmental and stool samples were conducted to determine the aetiology of the outbreak and the modes of transmission. The only commonality was the food, crockery and cutlery provided and/or handled by the hotel's Chinese banquet kitchen. Stool specimens from 34 cases and 15 food handlers were positive for norovirus genogroup II. The putative index case was one of eight norovirus-positive food handlers who had worked while they were symptomatic. Several food samples and remnants tested positive for Escherichia coli or high faecal coliforms, aerobic plate counts and/or total coliforms, indicating poor food hygiene. This large common-source outbreak of norovirus gastroenteritis was caused by the consumption of contaminated food and/or contact with contaminated crockery or cutlery provided or handled by the hotel's Chinese banquet kitchen.

Core Genome Multilocus Sequence Typing for Identification of Globally Distributed Clonal Groups and Differentiation of Outbreak Strains of Listeria monocytogenes.

ABSTRACTMany listeriosis outbreaks are caused by a few globally distributed clonal groups, designated clonal complexes or epidemic clones, of Listeria monocytogenes, several of which have been defined by classic multilocus sequence typing (MLST) schemes targeting 6 to 8 housekeeping or virulence genes. We have developed and evaluated core genome MLST (cgMLST) schemes and applied them to isolates from multiple clonal groups, including those associated with 39 listeriosis outbreaks. The cgMLST clusters were congruent with MLST-defined clonal groups, which had various degrees of diversity at the whole-genome level. Notably, cgMLST could distinguish among outbreak strains and epidemiologically unrelated strains of the same clonal group, which could not be achieved using classic MLST schemes. The precise selection of cgMLST gene targets may not be critical for the general identification of clonal groups and outbreak strains. cgMLST analyses further identified outbreak strains, including those associated with recent outbreaks linked to contaminated French-style cheese, Hispanic-style cheese, stone fruit, caramel apple, ice cream, and packaged leafy green salad, as belonging to major clonal groups. We further developed lineage-specific cgMLST schemes, which can include accessory genes when core genomes do not possess sufficient diversity, and this provided additional resolution over species-specific cgMLST. Analyses of isolates from different common-source listeriosis outbreaks revealed various degrees of diversity, indicating that the numbers of allelic differences should always be combined with cgMLST clustering and epidemiological evidence to define a listeriosis outbreak. IMPORTANCE Classic multilocus sequence typing (MLST) schemes targeting internal fragments of 6 to 8 genes that define clonal complexes or epidemic clones have been widely employed to study L. monocytogenes biodiversity and its relation to pathogenicity potential and epidemiology. We demonstrated that core genome MLST schemes can be used for the simultaneous identification of clonal groups and the differentiation of individual outbreak strains and epidemiologically unrelated strains of the same clonal group. We further developed lineage-specific cgMLST schemes that targeted more genomic regions than the species-specific cgMLST schemes. Our data revealed the genome-level diversity of clonal groups defined by classic MLST schemes. Our identification of U.S. and international outbreaks caused by major clonal groups can contribute to further understanding of the global epidemiology of L. monocytogenes.

An Economic Evaluation of PulseNet: A Network for Foodborne Disease Surveillance.

The PulseNet surveillance system is a molecular subtyping network of public health and food regulatory agency laboratories designed to identify and facilitate investigation of foodborne illness outbreaks. This study estimates health and economic impacts associated with PulseNet. The staggered adoption of PulseNet across the states offers a natural experiment to evaluate its effectiveness, which is measured as reduction of reported illnesses due to improved information, enhanced industry accountability, and more-rapid recalls. Economic impacts attributable to PulseNet include medical costs and productivity losses averted due to reduced illness. Program costs are also reported. Better information and accountability from enhanced surveillance is associated with large reductions of reported illnesses. Data collected between 1994 and 2009 were assembled and analyzed between 2010 and 2015. Conservatively, accounting for underreporting and underdiagnosis, 266,522 illnesses from Salmonella, 9,489 illnesses from Escherichia coli (E. coli), and 56 illnesses due to Listeria monocytogenes are avoided annually. This reduces medical and productivity costs by $507 million. Additionally, direct effects from improved recalls reduce illnesses from E. coli by 2,819 and Salmonella by 16,994, leading to $37 million in costs averted. Annual costs to public health agencies are $7.3 million. The PulseNet system makes possible the identification of food safety risks by detecting widespread or non-focal outbreaks. This gives stakeholders information for informed decision making and provides a powerful incentive for industry. Furthermore, PulseNet enhances the focus of regulatory agencies and limits the impact of outbreaks. The health and economic benefits from PulseNet and the foodborne disease surveillance system are substantial.

Molecular characterization of human Cryptosporidium spp. isolates after an unusual increase in late summer 2012.

BackgroundDuring the late summer 2012, a number of medical microbiological laboratories (MMLs) reported an unusual increase in cases of cryptosporidiosis, a gastrointestinal infection caused by the protozoan parasites Cryptosporidium spp. Prompted by this signal, the National Institute of Public Health and the Environment (RIVM) started an epidemiological investigation into possible causes. Simultaneously, samples diagnosed at MMLs were sent to RIVM for genotyping, aiming to further identify the possible source of the increase.MethodsGenotyping was performed by sequencing a fragment of the GP60 gene. Additional genotyping was performed on a subset of samples using six microsatellite markers. Population genetic analysis was performed using BEAST.ResultsThe majority of the samples were typed as C. hominis, and a single GP60 genotype (IbA10G2) largely predominated. Genotyping microsatellite markers further supported the circulation of a single genetic type. Population genetic analysis with genotypes found in previous years is inconsistent with a decrease in effective population size.ConclusionsThe conclusion of this finding is that the rise reflects more an overall increase and not a common source outbreak.

Fresh Produce–Associated Listeriosis Outbreaks, Sources of Concern, Teachable Moments, and Insights

Foodborne transmission of Listeria monocytogenes was first demonstrated through the investigation of the 1981 Maritime Provinces outbreak involving coleslaw. In the following two decades, most listeriosis outbreaks involved foods of animal origin, e.g., deli meats, hot dogs, and soft cheeses. L. monocytogenes serotype 4b, especially epidemic clones I, II, and Ia, were frequently implicated in these outbreaks. However, since 2008 several outbreaks have been linked to diverse types of fresh produce: sprouts, celery, cantaloupe, stone fruit, and apples. The 2011 cantaloupe-associated outbreak was one of the deadliest foodborne outbreaks in recent U.S. history. This review discusses produce-related outbreaks of listeriosis with a focus on special trends, unusual findings, and potential paradigm shifts. With the exception of sprouts, implicated produce types were novel, and outbreaks were one-time events. Several involved serotype 1/2a, and in the 2011 cantaloupe-associated outbreak, serotype 1/2b was for the first time conclusively linked to a common-source outbreak of invasive listeriosis. Also in this outbreak, for the first time multiple strains were implicated in a common-source outbreak. In 2014, deployment of whole genome sequencing as part of outbreak investigation validated this technique as a pivotal tool for outbreak detection and speedy resolution. In spite of the unusual attributes of produce-related outbreaks, in all but one of the investigated cases (the possible exception being the coleslaw outbreak) contamination was traced to the same sources as those for outbreaks associated with other vehicles (e.g., deli meats), i.e., the processing environment and equipment. The public health impact of farm-level contamination remains uncharacterized. This review highlights knowledge gaps regarding virulence and other potentially unique attributes of produce outbreak strains, the potential for novel fresh produce items to become unexpectedly implicated in outbreaks, and the key role of good control strategies in the processing environment.

Viral excretion and antibody titers in children infected with hepatitis A virus from an orphanage in western India

BackgroundHepatitis A is endemic in India and mainly causes sporadic infections. However, children in childcare centers, schools and orphanages are vulnerable to common-source outbreaks as they have naive hosts. ObjectivesTo investigate hepatitis A outbreak in an orphanage from Pune, India. Study DesignMonitoring of virus excretion and anti-HAV antibody levels in hepatitis A virus (HAV) infected children. ResultsThe orphanage housed 93 children of the age 1 month-6.5 years. Analysis of the collected serum (n=78) and stool samples (n=63) revealed 20 children to be either positive for anti-HAV IgM antibodies or excreting HAV, 14 being symptomatic and 6 asymptomatic, while 32 were already anti-HAV IgG positive either due to past HAV exposure (n=7, mean log antibody titers: 2.96) or maternal antibodies (n=25, mean log antibody titers: 1.13). Serum samples, taken 4 weeks apart, did not show any significant difference in the IgM and IgG antibody levels either. However, virus excretion decreased significantly after 15 days in symptomatic children (mean log HAV RNA copies/ml 1.03+0.30), while asymptomatic children continued to excrete higher viral loads, at constant levels (mean log HAV RNA copies/ml 2.33+0.33), for up to 90 days. ConclusionsThough virus excretion continued up to 90 days in all HAV infected children, asymptomatic children excreted higher viral loads for longer period and hence can contribute significantly in person-to-person virus transmission. All children should be vaccinated in such set ups.

Brief Report

Few previous studies have investigated the association between the severity of an infectious disease and the length of incubation period. We estimated the association between the length of the incubation period and the severity of infection with the severe acute respiratory syndrome coronavirus, using data from the epidemic in 2003 in Hong Kong. We estimated the incubation period of severe acute respiratory syndrome based on a subset of patients with available data on exposure periods and a separate subset of patients in a putative common source outbreak, and we found associations between shorter incubation period and greater severity in both groups after adjusting for potential confounders. Our findings suggest that patients with a shorter incubation period went on to have more severe disease. Further studies are needed to investigate potential biological mechanisms for this association.

A Common Source Outbreak of Severe Delirium Associated with Exposure to the Novel Synthetic Cannabinoid ADB-PINACA

BackgroundSince 2009, synthetic cannabinoid (SC) use has emerged as a growing public health threat in the United States (US). Several outbreaks of unexpected, severe toxicity linked to SC use have been reported since 2012. Reports of varied and significant morbidity after SC use are expected to increase because newer compounds enter the marketplace more frequently as manufacturers attempt to circumvent regulatory efforts. Case ReportWe report a cluster of 7 patients who experienced a spectrum of anxiety, delirium, psychosis, and aggressive behaviors after smoking the same SC-containing product at a party. An 8th patient with the same exposure source presented with delayed onset seizures. Biologic samples were analyzed for novel, newly identified SCs belonging to the FUBINACA family of compounds. A previously unknown SC, N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-pentyl-1H-indazole-3-carboxamide (ADB-PINACA) was identified in biologic samples from 7 of the individuals. ADB-PINACA was identified in the SC-containing product (“Crazy Clown”) seized by law enforcement and identified as the product smoked by the 8 patients in the reported cluster. Why Should an Emergency Physician Be Aware of This?The information compiled using this cluster of cases, and a similar reported outbreak of altered mental status in Colorado, implicating the same SC (ADB-PINACA) and brands of SC-containing products, aided the US Drug Enforcement Administration in its temporary scheduling of ADB-PINACA and three other SCs. In this outbreak, close cooperation between public health and law enforcement allowed for a rapid intervention, which halted the outbreak by interrupting the common source and accelerated regulatory efforts to prevent further morbidity and mortality.

Multistate foodborne hepatitis A outbreak among European tourists returning from Egypt– need for reinforced vaccination recommendations, November 2012 to April 2013

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Comparative genomic analysis of clinical and environmental Vibrio vulnificus isolates revealed biotype 3 evolutionary relationships.

In 1996 a common-source outbreak of severe soft tissue and bloodstream infections erupted among Israeli fish farmers and fish consumers due to changes in fish marketing policies. The causative pathogen was a new strain of Vibrio vulnificus, named biotype 3, which displayed a unique biochemical and genotypic profile. Initial observations suggested that the pathogen erupted as a result of genetic recombination between two distinct populations. We applied a whole genome shotgun sequencing approach using several V. vulnificus strains from Israel in order to study the pan genome of V. vulnificus and determine the phylogenetic relationship of biotype 3 with existing populations. The core genome of V. vulnificus based on 16 draft and complete genomes consisted of 3068 genes, representing between 59 and 78% of the whole genome of 16 strains. The accessory genome varied in size from 781 to 2044 kbp. Phylogenetic analysis based on whole, core, and accessory genomes displayed similar clustering patterns with two main clusters, clinical (C) and environmental (E), all biotype 3 strains formed a distinct group within the E cluster. Annotation of accessory genomic regions found in biotype 3 strains and absent from the core genome yielded 1732 genes, of which the vast majority encoded hypothetical proteins, phage-related proteins, and mobile element proteins. A total of 1916 proteins (including 713 hypothetical proteins) were present in all human pathogenic strains (both biotype 3 and non-biotype 3) and absent from the environmental strains. Clustering analysis of the non-hypothetical proteins revealed 148 protein clusters shared by all human pathogenic strains; these included transcriptional regulators, arylsulfatases, methyl-accepting chemotaxis proteins, acetyltransferases, GGDEF family proteins, transposases, type IV secretory system (T4SS) proteins, and integrases. Our study showed that V. vulnificus biotype 3 evolved from environmental populations and formed a genetically distinct group within the E-cluster. The unique epidemiological circumstances facilitated disease outbreak and brought this genotype to the attention of the scientific community.

Case study of the use of pulsed field gel electrophoresis in the detection of a food-borne outbreak.

In early July 2008, a cluster of six Salmonella Agona was identified in the Republic of Ireland. A dispersed, common source outbreak was suspected. Later in July a further case was identified and the Health Protection Agency in the UK indicated that they had 32 cases of S. Agona since Feb 2008. This chapter discusses how pulsed field gel electrophoresis was used to help confirm an outbreak and to trace the source of the outbreak.

Epidemiological profile of the Ebola virus disease outbreak in Nigeria, July-September 2014.

IntroductionIn July 2014, Nigeria experienced an outbreak of Ebola virus disease following the introduction of the disease by an ill Liberian Traveler. The Government of Nigeria with the support of Technical and Development Partners responded quickly and effectively to contain the outbreak. The epidemiological profile of the outbreak that majorly affected two States in the country in terms of person, place and time characteristics of the cases identified is hereby described.MethodsUsing field investigation technique, all confirmed and probable cases were identified, line-listed and analysed using Microsoft Excel 2007 by persons, time and place.ResultsA total of 20 confirmed and probable cases; 16 in Lagos (including the index case from Liberia) and 4 in Port Harcourt were identified. The mean age was 39.5 ± 12.4 years with over 40% within the age group 30-39 years. The most frequent exposure type was direct physical contact in 70% of all cases and 73% among health care workers. The total case-fatality was 40%; higher among healthcare workers (46%) compared with non-healthcare workers (22%). The epidemic curve initially shows a typical common source outbreak, followed by a propagated pattern.ConclusionInvestigation revealed the size and spread of the outbreak and provided information on the characteristics of persons, time and place. Enhanced surveillance measures, including contact tracing and follow- up proved very useful in early case detection and containment of the outbreak.

Investigating a community-wide outbreak of hepatitis a in India.

Background:There was an outbreak of acute hepatitis in Mylapore village, Kollam district, Kerala, southern India during February to June 2013. An outbreak investigation was initiated with the objective of describing the epidemiological features of the hepatitis outbreak.Materials and Methods:House-to-house visits were undertaken to identify symptomatic cases. The outbreak was described in terms of person, place and time. Hypothesis was generated based on findings from descriptive study, laboratory investigation of water samples, and environmental observations. A case-control study was designed to test the hypothesis. Chi-square test, univariate analysis, and logistic regression to identify the risk factors associated with hepatitis A infection were done.Results:Line list generated consisted of 45 cases. Attack rate was the highest among the age group 15-24 years (4.6%) followed by 5-14 years (3.1%). The geographical distribution of the cases suggested a clustering around the water supply through the pipeline and epidemic curve showed a sharp rise in cases suggestive of a common source outbreak. Water samples collected form pipeline showed evidence of fecal contamination and absence of residual chlorine. In the case-control study, having consumed water from the pipeline (odds ratio: 9.01 [95% confidence interval: 2.16-37.61]) was associated with the hepatitis A cases.Conclusion:The time frame of disease occurrence, environmental observations, anecdotal evidences, laboratory results and results of the analytical study indicated the possibility of occurrence of hepatitis A outbreak as a result of pipe water contamination supplied from a bore well. The study warrants establishment of an efficient water quality surveillance system.

A Mariner Transposon-Based Signature-Tagged Mutagenesis System for the Analysis of Oral Infection by Listeria monocytogenes

Listeria monocytogenes is a Gram-positive foodborne pathogen and the causative agent of listerosis a disease that manifests predominately as meningitis in the non-pregnant individual or infection of the fetus and spontaneous abortion in pregnant women. Common-source outbreaks of foodborne listeriosis are associated with significant morbidity and mortality. However, relatively little is known concerning the mechanisms that govern infection via the oral route. In order to aid functional genetic analysis of the gastrointestinal phase of infection we designed a novel signature-tagged mutagenesis (STM) system based upon the invasive L. monocytogenes 4b serotype H7858 strain. To overcome the limitations of gastrointestinal infection by L. monocytogenes in the mouse model we created a H7858 strain that is genetically optimised for oral infection in mice. Furthermore our STM system was based upon a mariner transposon to favour numerous and random transposition events throughout the L. monocytogenes genome. Use of the STM bank to investigate oral infection by L. monocytogenes identified 21 insertion mutants that demonstrated significantly reduced potential for infection in our model. The sites of transposon insertion included lmOh7858_0671 (encoding an internalin homologous to Lmo0610), lmOh7858_0898 (encoding a putative surface-expressed LPXTG protein homologous to Lmo0842), lmOh7858_2579 (encoding the HupDGC hemin transport system) and lmOh7858_0399 (encoding a putative fructose specific phosphotransferase system). We propose that this represents an optimised STM system for functional genetic analysis of foodborne/oral infection by L. monocytogenes.

Investigation into a Series of Mycobacterium Lentiflavum Bronchoalveolar Lavage Cultures

On June 28, 2012, Laboratory Medicine notified Infection Prevention of three positive Mycobacterium lentiflavum bronchoalveolar lavage (BAL) cultures obtained from three patients. These patients underwent bronchoscopy during the month of May (5/9, 5/15 & 5/25). Disease is rare with Mycobacterium lentiflavum and the lab had not detected this organism in the preceding 12 months. The lab processes approximately 150 BAL specimens per month with over 50% from the bronchoscopy suite. Two different bronchoscopes were used on the three patients. An investigation to rule out a common source outbreak was initiated.

Epidemiological investigation of two parallel gastroenteritis outbreaks in school settings

BackgroundTwo parallel gastroenteritis outbreaks occurred in an elementary school and a neighboring kindergarten in Kilkis, Northern Greece in 2012. The aim of the study was the investigation of these two parallel outbreaks as well as their possible source.MethodsTwo retrospective cohort studies were performed to identify the mode and the vehicle of transmission as well as the possible connection between them.ResultsElementary school and kindergarten populations of 79.9% (119/149) and 51.1% (23/45) respectively, participated in the study. Case definition was satisfied by 65 pupils from the elementary school and 14 from the kindergarten. For elementary school, 53 cases were considered primary cases of the outbreak and were included in the analysis. Based on the results of the multivariate analysis, consumption of tap water was the only statistically significant independent risk factor of gastroenteritis (RR = 2.34, 95% C.I.: 1.55-3.53).; a finding supported by the shape of the epidemic curve which referred to a common point source outbreak with secondary cases. For kindergarten, no statistically significant risk factor was identified, and the epidemic curve supported a person-to-person transmission according univariate analysis. Norovirus GI and GII and human Adenovirus were detected by Real Time PCR in stool samples from seven children of elementary school, but stool samples were not collected by children of the kindergarten.ConclusionsEven though the etiological agent of the outbreak was not verified, combined epidemiological and laboratory results were in favor of a waterborne viral gastroenteritis outbreak at the elementary school, followed by a person to person spread at the kindergarten.