Listeria monocytogenes has been the most common microbial cause of cheese-related recalls in both the United States and Canada in recent years. Since L. monocytogenes is inactivated by pasteurization, the majority of these cases have been linked to environmental and cross-contamination of fresh-soft, soft-ripened, and semi-soft cheeses. Cross-contamination of foods with L. monocytogenes is a continuous risk throughout the food supply chain and presents unique challenges for subsequent illness and outbreak investigations. Reports on outbreaks of listeriosis attributed to cross-contamination downstream from primary processing help highlight the critical role of epidemiological investigation coupled with coordinated molecular subtyping and surveillance in the recognition and investigation of complex foodborne outbreaks. Despite their complexity, environmental sampling throughout the supply chain coupled with improved genotyping approaches and concomitant analysis of foodborne illness epidemiological exposure data are needed to help resolve these and similar cases more rapidly and with greater confidence.

Listeria monocytogenes is a foodborne pathogen that can cause bacteraemia, meningitis, and complications during pregnancy. In July 2012, molecular subtyping identified indistinguishable L. monocytogenes isolates from six patients and two samples of different cut and repackaged cheeses. A multistate outbreak investigation was initiated. Initial analyses identified an association between eating soft cheese and outbreak-related illness (odds ratio 17·3, 95% confidence interval 2·0–825·7) but no common brand. Cheese inventory data from locations where patients bought cheese and an additional location where repackaged cheese yielded the outbreak strain were compared to identify cheeses for microbiological sampling. Intact packages of imported ricotta salata yielded the outbreak strain. Fourteen jurisdictions reported 22 cases from March–October 2012, including four deaths and a fetal loss. Six patients ultimately reported eating ricotta salata; another reported eating cheese likely cut with equipment also used for contaminated ricotta salata, and nine more reported eating other cheeses that might also have been cross-contaminated. An FDA import alert and US and international recalls followed. Epidemiology-directed microbiological testing of suspect cheeses helped identify the outbreak source. Cross-contamination of cheese highlights the importance of using validated disinfectant protocols and routine cleaning and sanitizing after cutting each block or wheel.

During June–August 2013, 25 US states reported 631 cyclosporiasis cases including Nebraska and Iowa where a regional investigation implicated common-source imported salad mix served in two chain restaurants. At least two common-origin growing fields were likely sources of contaminated romaine lettuce. Using producer- and distributor-provided data, we conducted a grower-specific traceforward investigation to reveal exposures of ill US residents elsewhere who reported symptom onset during 11 June–1 July 2013, the time period established in the Nebraska and Iowa investigation. Romaine lettuce shipped on 2–6 June from one of these Mexico-origin growing fields likely caused cyclosporiasis in 78 persons reporting illness onsets from 11 June to 1 July in Nebraska, Texas, and Florida. Nationwide, 97% (314/324) of persons confirmed with cyclosporiasis with symptom onset from 11 June to 1 July 2013 resided in 11 central and eastern US states receiving approximately two-thirds of romaine lettuce from this field. This grower's production practices should be investigated to determine potential sources of contamination and to develop recommendations to prevent future illnesses.

In 2012 a US multistate outbreak of listeriosis was linked to ricotta salata imported from Italy, made from pasteurized sheep's milk. Sampling activities were conducted in Italy to trace the source of Listeria monocytogenes contamination. The cheese that caused the outbreak was produced in a plant in Apulia that processed semi-finished cheeses supplied by five plants in Sardinia. During an ‘emergency sampling’, 179 (23·6%) out of 758 end-products tested positive for L. monocytogenes, with concentrations from <10 c.f.u./g to 1·1 × 106 c.f.u./g. Positive processing environment samples were found in two out of four processing plants. A ‘follow-up sampling’ was conducted 8 months later, when environmental samples from three out of six plants tested positive for L. monocytogenes and for Listeria spp. PFGE subtyping showed 100% similarity between US clinical strains and isolates from ricotta salata, confirming the origin of the outbreak. The persistence of strains in environmental niches of processing plants was demonstrated, and is probably the cause of product contamination. Two PFGE profiles from clinical cases of listeriosis in Italy in 2011, stored in the MSS-TESSy database, were found to have 100% similarity to one PFGE profile from a US clinical case associated with the consumption of ricotta salata, according to the US epidemiological investigation (sample C, pulsotype 17). However, they had 87% similarity to the only PFGE profile found both in the US clinical case and in 14 ricotta cheese samples collected during the emergency sampling (sample B, pulsotype 1). Sharing of molecular data and availability of common characterization protocols were key elements that connected the detection of the US outbreak to the investigation of the food source in Italy. Simultaneous surveillance systems at both food and human levels are a necessity for the efficient rapid discovery of the source of an outbreak of L. monocytogenes.

Two cases of hospital-acquired listeriosis were linked to a commercially produced, pasteurized ice cream mix. Manufacturers should implement safety measures from the Food Safety Modernization Act to minimize the risk of Listeria contamination. Dietary guidelines for persons at high risk of listeriosis may need revision to recognize the potential risk from pasteurized products.

During one week in July 2012, two patients from the same ward at the municipal hospital in Vaasa, Finland, were diagnosed with septicaemia caused by Listeria monocytogenes. An outbreak investigation revealed eight concomitant cases of febrile gastroenteritis caused by L. monocytogenes on the same ward. Median age of the cases was 82 years and median incubation time for listerial gastroenteritis was 21 h (range 9–107). An additional 10 cases of invasive listeriosis caused by the same outbreak strain were identified across the whole country during the summer of 2012. Environmental investigation at the affected municipal hospital ward revealed ready-sliced meat jelly as the suspected source of the infection. During inspection of the meat jelly production plant, one pooled sample taken from a floor drain and a trolley wheel in the food processing environment was positive for the outbreak strain of L. monocytogenes. After the producer stopped the production of meat jelly, no further cases of listeriosis with the outbreak strain were identified via nationwide surveillance.

Although infection by the pathogenic bacterium Listeria monocytogenes is relatively rare, consequences can be severe, with a high case-fatality rate in vulnerable populations. A quantitative, probabilistic risk assessment tool was developed to compare estimates of the number of invasive listeriosis cases in vulnerable Canadian subpopulations given consumption of contaminated ready-to-eat delicatessen meats and hot dogs, under various user-defined scenarios. The model incorporates variability and uncertainty through Monte Carlo simulation. Processes considered within the model include cross-contamination, growth, risk factor prevalence, subpopulation susceptibilities, and thermal inactivation. Hypothetical contamination events were simulated. Results demonstrated varying risk depending on the consumer risk factors and implicated product (turkey delicatessen meat without growth inhibitors ranked highest for this scenario). The majority (80%) of listeriosis cases were predicted in at-risk subpopulations comprising only 20% of the total Canadian population, with the greatest number of predicted cases in the subpopulation with dialysis and/or liver disease. This tool can be used to simulate conditions and outcomes under different scenarios, such as a contamination event and/or outbreak, to inform public health interventions.

An acute gastroenteritis (AGE) outbreak was reported in May 2013 in Gyeonggi Province, South Korea. Eight students who had eaten breakfast on 21 May 2013 at a high-school restaurant exhibited AGE symptoms. Our case-control study showed that a strong association was observed between AGE symptoms and fermented oyster consumption. Virological studies also indicated that noroviruses (NoVs) were detected from both clinical samples and fermented oyster samples, and multiple different genotypes (genogroups GII.4, GII.11 and GII.14) of NoVs were present in both samples. The nucleotide sequence similarity between the strains found in the clinical samples and those in the fermented oysters was more than 99·5%. Therefore, to prevent further outbreaks, proper management of raw oysters is necessary and the food industry should be aware of the risk of viral gastroenteritis posed by fermented oysters contaminated with NoVs.

In November 2013, the Norwegian Institute of Public Health was notified of a gastroenteritis outbreak following two meetings held at a conference centre. Identical food and beverages were served during the meetings. We investigated in order to identify the vehicle of infection and implement control measures. Meeting participants completed an online questionnaire on consumption of foods and beverages. We asked symptomatic participants to provide a stool sample. We defined a case as diarrhoea and/or vomiting in a participant who became ill within 3 days after the meeting. We calculated attack rates (AR) and adjusted risk ratios (aRR) with 95% confidence intervals (CI) using binomial regression. We conducted environmental investigations. Overall, 147/168 (88%) participants responded, of which 74 (50%) met the case definition. All five stool samples provided were norovirus positive. No kitchen staff reported being sick. Risk of illness was higher in those who consumed raspberry mousse (aRR 3·4, 95% CI 1·4–8·2) and sliced fresh fruit (aRR 1·9, 95% CI 1·3–2·8). Seventy cases (95%) ate raspberry mousse. Frozen raspberries used for the mousse were imported and not heat-treated before consumption. Non-heat-treated frozen raspberries were the most likely outbreak vehicle. Contamination by a food handler could not be excluded. We recommend heat-treatment of imported frozen berries before consumption.

Gastroenteritis remains an important cause of morbidity and mortality worldwide. With the introduction of vaccines against rotavirus, interest has shifted to understanding the epidemiology of norovirus (NoV). While the importance of NoV in gastroenteritis outbreaks is well established, its role in sporadic gastroenteritis is less known. To better define the role of NoV as a cause of sporadic gastroenteritis we investigated its prevalence in the patients seen in our paediatric hospital with special emphasis on its seasonal and age distribution. Over a 12-month period discarded stool specimens submitted to our paediatric hospital for testing of an infectious aetiology were retrieved and additionally tested for NoV by real-time reverse transcriptase–polymerase chain reaction; demographical and clinical information were also obtained. Overall, NoV was the single most commonly identified pathogen and found in 68/892 (7·6%) total specimens or 68/258 (26%) of pathogen-positive specimens. The highest rates of NoV were detected in children aged 6 months to 4 years (50/332, 15·1%) and presenting between October and January (46/314, 14·7%). NoV has become the main cause of gastroenteritis in our paediatric population.

Rotavirus (RV) infection causes acute infantile diarrhoea in humans and animals and remains a major concern for vaccine development. The close proximity of humans to animals may foster cross-species infection resulting in the emergence of novel/unusual strains by genetic reassortment. In this study, we characterized 500 diarrhoeal samples for group A rotaviruses (RVA) from children (n = 290), piglets (n = 95) and calves (n = 115) in Northeast India during 2012–2013. The data showed that 142/500 (28·4%) faecal samples were positive for RVA with the highest level of infection detected in piglets (57/142, 40·1%) followed by children (51/142, 35·9%) and calves (34/142, 23·9%). Sequence-based G- and P-typing showed G1P[8] (25%) and G1P[7] (35%) were the prevailing genotypes in both humans and animals. Single cases of unusual genotypes, i.e. G9P[8], G5P[8] in humans and G1P[13], G1P[23] and G3P[7] in animals were also identified. Cluster analyses of the sequences showed regional strains were genetically closer to their homologous strains. However, human G5P[8] and porcine G1P[8] strains showed homology to heterologous hosts of their prototype strains. The subsequent global spread of unusual RV strains may result in their establishment over time, presenting challenges to future vaccine evaluation programmes. More studies on emerging genotypes are required to elucidate how RVA strains evolve post-vaccination. This study supports the need for continuous surveillance of RVA infections after detecting from diverse hosts in a common setting.

Giardia intestinalis is the leading parasitic aetiology of human enteric infections in the United States, with an estimated 1·2 million cases occurring annually. To better understand transmission, we analysed data on all giardiasis outbreaks reported to the Centers for Disease Control and Prevention for 1971–2011. The 242 outbreaks, affecting ~41 000 persons, resulted from waterborne (74·8%), foodborne (15·7%), person-to-person (2·5%), and animal contact (1·2%) transmission. Most (74·6%) waterborne outbreaks were associated with drinking water, followed by recreational water (18·2%). Problems with water treatment, untreated groundwater, and distribution systems were identified most often during drinking water-associated outbreak investigations; problems with water treatment declined after the 1980s. Most recreational water-associated outbreaks were linked to treated swimming venues, with pools and wading pools implicated most often. Produce was implicated most often in foodborne outbreaks. Additionally, foods were most commonly prepared in a restaurant and contaminated by a food handler. Lessons learned from examining patterns in outbreaks over time can help prevent future disease. Groundwater and distribution system vulnerabilities, inadequate pool disinfection, fruit and vegetable contamination, and poor food handler hygiene are promising targets for giardiasis prevention measures.

In September 2011, a patient cluster with a rare Salmonella serotype – Strathcona – was identified in Denmark. An outbreak investigation was initiated to reveal the source in order to stop the outbreak. In addition to hypothesis-generating interviews, comparable analyses of patients’ household shopping receipts were conducted. A matched case-control study with 25 cases and 56 population register controls was conducted to test the findings of the hypothesis-generating investigation. In total, 43 cases of Salmonella Strathcona were reported in Denmark. Additionally, 28 cases were reported from Germany, Italy, Austria and Belgium. The results of the investigation in Denmark showed that 8/10 cases had bought datterino tomatoes prior to disease onset. Illness was associated with a specific supermarket chain [matched odds ratio (mOR) 16·9, 95% confidence interval (CI) 2·2–130], and having consumed elongated small tomatoes (OR 28·1, 95% CI 2·6–302). Traceback investigation showed that the tomatoes came from an Italian producer. This outbreak, linked to tomatoes, underpins the growing recognition of the broad source range of Salmonella and the ability of fresh produce to cause multi-country outbreaks. It is important to strengthen the international cooperation between public-health and food-safety authorities in the European Union to investigate future multi-country outbreaks in order to prevent illness from ready-to-eat produce.

Five cases of STEC O157 phage type (PT) 21/28 reported consumption of raw cows' drinking milk (RDM) produced at a dairy farm in the South West of England. STEC O157 PT21/28 was isolated from faecal specimens from milking cows on the implicated farm. Whole genome sequencing (WGS) showed that human and cattle isolates were the same strain. Further analysis of WGS data confirmed that sequences of isolates from an additional four cases (who did not report consumption of RDM when first questioned) fell within the same five single nucleotide polymorphism cluster as the initial five cases epidemiologically linked to the consumption of RDM. These four additional cases identified by WGS were investigated further and were, ultimately, associated with the implicated farm. The RDM outbreak strain encoded stx2a, which is associated with increased pathogenicity and severity of symptoms. Further epidemiological analysis showed that 70% of isolates within a wider cluster containing the outbreak strain were from cases residing in, or linked to, the same geographical region of England. During this RDM outbreak, use of WGS improved case ascertainment and provided insights into the evolution of a highly pathogenic clade of STEC O157 PT21/28 stx2a associated with the South West of England.

Pathogens utilize type III secretion systems to deliver effector proteins, which facilitate bacterial infections. The Escherichia coli type III secretion system 2 (ETT2) which plays a crucial role in bacterial virulence, is present in the majority of E. coli strains, although ETT2 has undergone widespread mutational attrition. We investigated the distribution and characteristics of ETT2 in avian pathogenic E. coli (APEC) isolates and identified five different ETT2 isoforms, including intact ETT2, in 57·6% (141/245) of the isolates. The ETT2 locus was present in the predominant APEC serotypes O78, O2 and O1. All of the ETT2 loci in the serotype O78 isolates were degenerate, whereas an intact ETT2 locus was mostly present in O1 and O2 serotype strains, which belong to phylogenetic groups B2 and D, respectively. Interestingly, a putative second type III secretion-associated locus (eip locus) was present only in the isolates with an intact ETT2. Moreover, ETT2 was more widely distributed in APEC isolates and exhibited more isoforms compared to ETT2 in human extraintestinal pathogenic E. coli, suggesting that APEC might be a potential risk to human health. However, there was no distinct correlation between ETT2 and other virulence factors in APEC.

In Sweden, acute gastrointestinal illness (AGI) incidence, severity, impact on productivity, related healthcare usage and associated costs are not ascertained. We measured these in 2013–2014 using a population-based cohort reporting weekly. We defined AGI as ⩾3 episodes of loose stools or vomiting/24 h; or loose stools or vomiting with ⩾2 other gastrointestinal symptoms. After each AGI episode, we collected information about perceived severity, healthcare use and absenteeism. We calculated incidence rates, AGI absenteeism and costs comprising direct healthcare costs and productivity loss due to work/school absenteeism. A total of 3241 participants reported 1696 AGI episodes [incidence 360/1000 person-years, 95% confidence interval (CI) 326–395; highest in the <5 years age group]. In the <5 years age group, 31% of episodes were perceived as mild, 61% as moderate and 8% as severe; 9·4% led to primary-care consultations, and 1·4% to hospital admissions. In the ⩾5 years age group, 18% of episodes were perceived as mild, 64% as moderate and 18% as severe; 6·4% led to primary-care consultations, and 1·9% to hospital admissions. AGI caused 8 891 000 days of absenteeism (95% CI 6 009 000–12 780 000). AGI cost €1 005 885 000 (95% CI 754 309 000–1 257 195 000) nationally for the year. In Sweden, a minority of cases perceive AGI as a mild illness. AGI is a burden on the healthcare system and causes productivity loss, with high costs. Countries may consider these estimates when prioritizing health interventions.

In August 2013, a nationwide vaccination campaign with bivalent oral polio vaccine (bOPV) was initiated after isolation of wild-type poliovirus type 1 (WPV-1) in routine sewage surveillance in Israel. The campaign started in the Southern district and later extended to the entire country. This study examined the association between socioeconomic status (SES), and compliance with bOPV vaccine during the campaign. Nationwide data relating to SES by geographical cluster were correlated with vaccine coverage rates in the same areas. All analyses were conducted separately for Jews and Arabs. Coverage with the bOPV vaccination campaign in the Arab population (92·4%) was higher than in the Jewish population (59·2%). This difference was consistently present in all SES clusters. In the Jewish population there was an inverse correlation between SES and vaccination coverage rates (R = −0·93, P < 0·001). Lower vaccination coverage with supplemental vaccine activities in higher SES groups is a challenge that needs to be addressed in future public health events and emergencies in order to achieve satisfactory protection rates for the public.

The Middle East region is plagued with repeated armed conflicts that affect both civilians and soldiers. Injuries sustained during war are common and frequently associated with multiple life-threatening complications. Wound infections are major consequences of these war injuries. The microbiology of war-related wound infections is variable with predominance of Gram-negative bacteria in later stages. The emergence of antimicrobial resistance among isolates affecting war-related wound injuries is a serious problem with major regional and global implications. Factors responsible for the increase in multidrug-resistant pathogens include timing and type of surgical management, wide use of antimicrobial drugs, and the presence of metallic or organic fragments in the wound. Nosocomial transmission is the most important factor in the spread of multidrug-resistant pathogens. Wound management of war-related injuries merits a multidisciplinary approach. This review aims to describe the microbiology of war-related wound infections and factors affecting their incidence from conflict areas in Iraq, Syria, Israel, and Lebanon.

Pneumonia is a leading cause of mortality and morbidity worldwide with radiographically confirmed pneumonia a key disease burden indicator. This is usually determined by a radiology panel which is assumed to be the best available standard; however, this assumption may introduce bias into pneumonia incidence estimates. To improve estimates of radiographic pneumonia incidence, we applied Bayesian latent class modelling (BLCM) to a large database of hospitalized patients with acute lower respiratory tract illness in Sa Kaeo and Nakhon Phanom provinces, Thailand from 2005 to 2010 with chest radiographs read by both a radiology panel and a clinician. We compared these estimates to those from conventional analysis. For children aged <5 years, estimated radiographically confirmed pneumonia incidence by BLCM was 2394/100 000 person-years (95% credible interval 2185–2574) vs. 1736/100 000 person-years (95% confidence interval 1706–1766) from conventional analysis. For persons aged ⩾5 years, estimated radiographically confirmed pneumonia incidence was similar between BLCM and conventional analysis (235 vs. 215/100 000 person-years). BLCM suggests the incidence of radiographically confirmed pneumonia in young children is substantially larger than estimated from the conventional approach using radiology panels as the reference standard.

Historical survey data suggest that the seroprevalence of antibodies against Coxiella burnetii in the general population of The Netherlands decreased from more than 40% in 1983 to 2·4% in 2007, just before the start of the large 2007–2010 Q fever epidemic. To assess whether the sharp decline in seroprevalence was real, we performed a cross-sectional study using historical samples. We tested samples using a contemporary commercial indirect immunofluorescence assay. In plasma samples from the south of The Netherlands from 1987, we found an age- and sex-standardized seroprevalence of 14·4% (95% confidence interval 11·2–18·3). This was significantly lower than a 1983 estimate from the same area (62·5%), but significantly higher than 2008 (1·0%) and 2010 (2·3%) estimates from the same area. The study suggests that there was a steady and sharp decline in Q fever seroprevalence in the south of The Netherlands from 1987 to 2008. We assume that seroprevalence has decreased in other parts of The Netherlands as well and seroprevalence surveys in other European countries have shown a similar declining trend. Waning population immunity in The Netherlands may have contributed to the scale of the 2007–2010 Q fever epidemic. For a better understanding of the infection dynamics of Q fever, we advocate an international comparative study of the seroprevalence of C. burnetii.