From Foodborne Disease Outbreak (FBDO) to Investigation: The Plant Toxin Trap, Brittany, France, 2018

On 6 July 2018, the Center for Epidemiology and Public Health of the French Armed Forces was informed of an outbreak of acute gastroenteritis among customers of a dining facility at a military base in Brittany, France. A total of 200 patients were reported out of a population of 1700 (attack rate: 12%). The symptoms were mainly lower digestive tract disorders and occurred rapidly after lunch on 5 July (median incubation period: 3.3 h), suggesting a toxin-like pathogenic process. A case-control survey was carried out (92 cases and 113 controls). Statistical analysis pointed to the chili con carne served at lunch on 5 July as the very likely source of poisoning. Phytohaemagglutinin, a plant lectin, was found in the chili con carne at a concentration above the potentially toxic dose (400 HAU/gram). The raw kidney beans incorporated in the chili con carne presented a high haemagglutination activity (66,667 HAU/gram). They were undercooked, and the phytohaemagglutinin was not completely destroyed. FBDOs due to PHA are poorly documented. This study highlights the need to develop methods for routine testing of plant toxins in food matrices. Improved diagnostic capabilities would likely lead to better documentation, epidemiology, and prevention of food-borne illnesses caused by plant toxins.

Cryptosporidiosis outbreaks linked to the public water supply in a military camp, France

Introduction

Contaminated drinking and recreational waters account for most of the reported Cryptosporidium spp. exposures in high-income countries. In June 2017, two successive cryptosporidiosis outbreaks occurred among service members in a military training camp located in Southwest France. Several other gastroenteritis outbreaks were previously reported in this camp, all among trainees in the days following their arrival, without any causative pathogen identification. Epidemiological, microbiological and environmental investigations were carried out to explain theses outbreaks.

Material and methods

Syndromic diagnosis using multiplex PCR was used for stool testing. Water samples (100 L) were collected at 10 points of the drinking water installations and enumeration of Cryptosporidium oocysts performed. The identification of Cryptosporidium species was performed using real-time 18S SSU rRNA PCR and confirmed by GP60 sequencing.

Results

A total of 100 human cases were reported with a global attack rate of 27.8%. Cryptosporidium spp. was identified in 93% of stool samples with syndromic multiplex PCR. The entire drinking water network was contaminated with Cryptosporidium spp. The highest level of contamination was found in groundwater and in the water leaving the treatment plant, with >1,000 oocysts per 100 L. The same Cryptosporidium hominis isolate subtype IbA10G2 was identified in patients’ stool and water samples. Several polluting activities were identified within the protection perimeters of the water resource. An additional ultrafiltration module was installed at the outlet of the water treatment plant. After several weeks, no Cryptosporidium oocysts were found in the public water supply.

Conclusions

After successive and unexplained gastroenteritis outbreaks, this investigation confirmed a waterborne outbreak due to Cryptosporidium hominis subtype IbA10G2. Our study demonstrates the value of syndromic diagnosis for gastroenteritis outbreak investigation. Our results also highlight the importance of better assessing the microbiological risk associated with raw water and the need for sensitive and easy-to-implement tools for parasite detection.

Cryptosporidiosis remains a neglected infectious disease, even in high-income countries. Most of the reported cases and outbreaks are related to drinking water and recreational water contaminated with Cryptosporidium spp. In Europe, the search for Cryptosporidium spp. and other parasites in stool or water samples is not routinely performed by laboratories, especially in the absence of dedicated national guidance on testing. In France, cryptosporidiosis is not a notifiable disease. In order to better assess the pathogens involved in foodborne and waterborne disease outbreaks a new outbreak investigation strategy was implemented in the French Armed Forces including: systematic stool sampling, routine syndromic multiplex PCR diagnoses, and pathogens genotyping. After several unexplained gastroenteritis outbreaks in a military camp in France, we identified the same C. hominis IbA10G2 isolate in the stools of patients and in the entire water distribution network. The highest levels of contamination were found in groundwater and in the water leaving the treatment plant. Our study demonstrates the value of syndromic diagnosis for gastroenteritis outbreaks investigation and highlights the importance of better assessing the microbiological risks associated with raw water.

Assessment of Food and Waterborne Viral Outbreaks by Using Field Epidemiologic, Modern Laboratory and Statistical Methods-Lessons Learnt from Seven Major Norovirus Outbreaks in Finland

Seven major food- and waterborne norovirus outbreaks in Western Finland during 2014–2018 were re-analysed. The aim was to assess the effectiveness of outbreak investigation tools and evaluate the Kaplan criteria. We summarised epidemiological and microbiological findings from seven outbreaks. To evaluate the Kaplan criteria, a one-stage meta-analysis of data from seven cohort studies was performed. The case was defined as a person attending an implicated function with diarrhoea, vomiting or two other symptoms. Altogether, 22% (386/1794) of persons met the case definition. Overall adjusted, 73% of norovirus patients were vomiting, the mean incubation period was 44 h (4 h to 4 days) and the median duration of illness was 46 h. As vomiting was a more common symptom in children (96%, 143/149) and diarrhoea among the elderly (92%, 24/26), symptom and age presentation should drive hypothesis formulation. The Kaplan criteria were useful in initial outbreak assessments prior to faecal results. Rapid food control inspections enabled evidence-based, public-health-driven risk assessments. This led to probability-based vehicle identification and aided in resolving the outbreak event mechanism rather than implementing potentially ineffective, large-scale public health actions such as the withdrawal of extensive food lots. Asymptomatic food handlers should be ideally withdrawn from high-risk work for five days instead of the current two days. Food and environmental samples often remain negative with norovirus, highlighting the importance of research collaborations. Electronic questionnaire and open-source novel statistical programmes provided time and resource savings. The public health approach proved useful within the environmental health area with shoe leather field epidemiology, combined with statistical analysis and mathematical reasoning.

Interaction between norovirus and Histo-Blood Group Antigens: A key to understanding virus transmission and inactivation through treatments?

Human noroviruses (HuNoVs) are a main cause of acute gastroenteritis worldwide. They are frequently involved in foodborne and waterborne outbreaks. Environmental transmission of the virus depends on two main factors: the ability of viral particles to remain infectious and their adhesion capacity onto different surfaces. Until recently, adhesion of viral particles to food matrices was mainly investigated by considering non-specific interactions (e.g. electrostatic, hydrophobic) and there was only limited information about infectious HuNoVs because of the absence of a reliable in vitro HuNoV cultivation system. Many HuNoV strains have now been described as having specific binding interactions with human Histo-Blood Group Antigens (HBGAs) and non-HBGA ligands found in food and the environment. Relevant approaches to the in vitro replication of HuNoVs were also proposed recently. On the basis of the available literature data, this review discusses the opportunities to use this new knowledge to obtain a better understanding of HuNoV transmission to human populations and better evaluate the hazard posed by HuNoVs in foodstuffs and the environment.

An outbreak of norovirus infection caused by ice cubes and a leaking air ventilation valve

A gastrointestinal outbreak was reported among 154 diners who attended a Christmas buffet on the 9 and 10 December 2016. A retrospective cohort study was undertaken. Faecal samples, water, ice and an air ventilation device were tested for indicators and routine pathogens. Altogether 26% (24/91) fulfilled the case definition of having typical viral gastrointestinal symptoms. Norovirus genogroup I was detected in faecal samples from three cases. One of these cases tested positive also for sapovirus and had a family member testing positive for both norovirus and sapovirus. A diner who drank water or drinks with ice cubes (risk ratios (RR) 6.5, 95% confidence intervals (CI) 1.5–113.0) or both (RR 8.2, 95% CI 1.7–145.5) had an increased risk in a dose-response manner. Ice cubes from three vending machines had high levels of heterotrophic bacteria. A faulty air ventilation valve in the space where the ice cube machine was located was considered a likely cause of this outbreak. Leaking air ventilation valves may represent a neglected route of transmission in viral gastrointestinal outbreaks.

Norovirus GII.17 Outbreak Linked to an Infected Post-Symptomatic Food Worker in a French Military Unit Located in France

In February 2016, an outbreak of gastroenteritis occurred in a French military unit located in Poitiers, France. Attack rate was of 34% (103/300). A case-control study identified association between illness and cake consumption. Stool samples were tested positive for Norovirus GII.17 for one patient and one post-symptomatic food worker (FW). The FW presented vomiting one day before cake preparation. The NoV strain was probably spread through food worker hand contact. Prevention of Norovirus foodborne outbreaks implies new guidelines for FWs management in France and Europe.

A norovirus GII.P21 outbreak in a boarding school, Austria 2014

OBJECTIVES

An Austrian boarding school reported a cluster of gastroenteritis on January 10, 2014. Environmental swabs from the school cafeteria and a nearby kebab restaurant tested positive for norovirus. The outbreak was investigated to identify its source(s).

METHODS

An outbreak case was defined as a student or staff member with diarrhoea or vomiting that developed between January 7 and 13. Details on food exposure were collected via a self-administered questionnaire; risk ratios (RR) and 95% confidence intervals (CI) were calculated. Norovirus from the stool specimens of cases and asymptomatic kebab restaurant workers were genotyped.

RESULTS

Twenty-eight cases were identified among 144 persons (attack rate 19%). The outbreak emerged and peaked on January 9, and ended on January 12. Compared to those who did not eat kebab, those who ate kebab on 7, 8, and 9 January were respectively 11 (95% CI 4.2-28), 6.7 (95% CI 3.4-13), and 9.3 (95% CI 4.0-22) times more likely to develop disease within the following 2 days. Stool specimens from three cases and three restaurant workers were positive for norovirus GII.P21.

CONCLUSIONS

The kebab prepared by norovirus-positive restaurant workers was the most likely source of the outbreak. It is recommended that food handlers comply strictly with hand hygiene and avoid bare-handed contact with ready-to-eat food to minimize the risk of food-borne infection.

Prevention of infectious diseases during military deployments: a review of the French armed forces strategy

Military personnel in operations have always paid a high toll to infections. In the 21st century some of these diseases still cause outbreaks with significant morbidity and impact on deployments. The new configuration of the French Armed Forces requires the permanent preparedness of deployable units. During deployments, soldiers are at least exposed to the infectious diseases that are observed in travellers, but with a potentially severe impact for the combatting strengths and a risk for cancelation or failure of the operational durability. The most common disabling infections during military deployments are faeco-oral transmitted diseases including diarrhoea. Preventing infectious diseases during deployments is of great concern and the French medical service has established a strategy based on different components; risk assessment and preparation, immunizations, protective measures and chemoprophylaxis, health education, health surveillance, outbreak investigations and medical tracking. In this review, the authors present the context of deployment of the French Armed Forces, the main health risks they are exposed to and develop the key points of the force health protection strategy, focused on infections related to military deployments.