Tiefkühlfrüchte als Risikofaktor für Gastroenteritis-Ausbrüche durch Noroviren

Natural Host-Environmental Media-Human: A New Potential Pathway of COVID-19 Outbreak

Identifying the first infected case (patient zero) is key in tracing the origin of a virus; however, doing so is extremely challenging. Patient zero for coronavirus disease 2019 (COVID-19) is likely to be permanently unknown. Here, we propose a new viral transmission route by focusing on the environmental media containing viruses of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or RaTG3-related bat-borne coronavirus (Bat-CoV), which we term the "environmental quasi-host." We reason that the environmental quasi-host is likely to be a key node in helping recognize the origin of SARS-CoV-2; thus, SARS-CoV-2 might be transmitted along the route of natural host-environmental media-human. Reflecting upon viral outbreaks in the history of humanity, we realize that many epidemic events are caused by direct contact between humans and environmental media containing infectious viruses. Indeed, contacts between humans and environmental quasi-hosts are greatly increasing as the space of human activity incrementally overlaps with animals' living spaces, due to the rapid development and population growth of human society. Moreover, viruses can survive for a long time in environmental media. Therefore, we propose a new potential mechanism to trace the origin of the COVID-19 outbreak.

Outbreaks, occurrence, and control of norovirus and hepatitis a virus contamination in berries: A review

Foodborne enteric viruses, in particular HuNoV and HAV, are the most common cause of the berry-linked viral diseases, and outbreaks around the world, and have become an important concern for health authorities. Despite the increased importance of berry fruits as a vehicle for foodborne viruses, there is limited information concerning the fate of foodborne viruses in the berry supply chain from farm to consumer. A comprehensive understanding of berry-associated viral outbreaks - with a focus on contamination sources, persistence, survival, and the effects of current postharvest and processing interventions and practices - is essential for the development of effective preventative strategies to reduce risk of illness. The purpose of this paper is twofold; (i) to critically review the published literature on the current state of knowledge regarding berry-associated foodborne viral outbreaks and the efficiency of berry processing practices and (ii) to identify and prioritize research gaps regarding practical and effective mechanism to reduce viral contamination of berries. The review found that fecally infected food handlers were the predominant source of preharvest and postharvest pathogenic viral contamination. Current industrial practices applied to fresh and frozen berries demonstrated limited efficacy for reducing the viral load. While maintaining best practice personal and environmental hygiene is a key intervention, the optimization of processing parameters (i.e., freezing, frozen storage, and washing) and/or development of alternative processing technologies to induce sufficient viral inactivation in berries along with retaining sensory and nutritional quality, is also an important direction for further research.

Microbial Contamination of Fresh Produce: What, Where, and How?

Promotion of healthier lifestyles has led to an increase in consumption of fresh produce. Such foodstuffs may expose consumers to increased risk of foodborne disease, as often they are not subjected to processing steps to ensure effective removal or inactivation of pathogenic microorganisms before consumption. Consequently, reports of ready-to-eat fruit and vegetable related disease outbreak occurrences have increased substantially in recent years, and information regarding these events is often not readily available. Identifying the nature and source of microbial contamination of these foodstuffs is critical for developing appropriate mitigation measures to be implemented by food producers. This review aimed to identify the foodstuffs most susceptible to microbial contamination and the microorganisms responsible for disease outbreaks from information available in peer-reviewed scientific publications. A total of 571 outbreaks were identified from 1980 to 2016, accounting for 72,855 infections and 173 deaths. Contaminated leafy green vegetables were responsible for 51.7% of reported outbreaks. Contaminated soft fruits caused 27.8% of infections. Pathogenic strains of Escherichia coli and Salmonella, norovirus, and hepatitis A accounted for the majority of cases. Large outbreaks resulted in particular biases such as the observation that contaminated sprouted plants caused 31.8% of deaths. Where known, contamination mainly occurred via contaminated seeds, water, and contaminated food handlers. There is a critical need for standardized datasets regarding all aspects of disease outbreaks, including how foodstuffs are contaminated with pathogenic microorganisms. Providing food business operators with this knowledge will allow them to implement better strategies to improve safety and quality of fresh produce.

Analysis of frozen strawberries involved in a large norovirus gastroenteritis outbreak using next generation sequencing and digital PCR

Virus-contaminated frozen berries have been frequently identified as cause of foodborne disease outbreaks. To provide new tools for virus detection and characterization in berries, next generation sequencing (NGS) and reverse transcription-digital PCR (RT-dPCR) techniques were tested here with strawberries previously involved in a large-scale norovirus (NoV) gastroenteritis outbreak in Germany. By NGS, about 29 million sequence reads were generated, which mainly showed identities to sequences from the plant matrix and from the bacterial flora. Most abundant virus sequences originated from plant-specific viruses, whereas sequences with high identity to human viruses were rare. Only two sequence reads showed homologies to human NoV. They were identical to GII.P16/GII.13 NoV sequences from patients and a strawberry sample independently analyzed during the outbreak. Quantification of the GII NoV RNA of the berries using RT-dPCR confirmed a low mean virus amount of 185 copies/25 g, which is similar to independently assessed RT-qPCR results (257 copies/25 g). The study shows that identification of human-pathogenic viruses in naturally contaminated frozen berries is possible using NGS technologies. However, the method needs to be further optimized in order to enable convenient and reproducible detection of a low amount of human-pathogenic virus sequences in a background of highly abundant nucleic acids of other sources.

Comparison and optimization of detection methods for noroviruses in frozen strawberries containing different amounts of RT-PCR inhibitors

Frozen berries have been repeatedly identified as vehicles for norovirus (NoV) transmission causing large gastroenteritis outbreaks. However, virus detection in berries is often hampered by the presence of RT-PCR-inhibiting substances. Here, several virus extraction methods for subsequent real-time RT-PCR-based NoV-RNA detection in strawberries were compared and optimized. NoV recovery rates (RRs) between 0.21 ± 0.13% and 10.29 ± 6.03% were found when five different artificially contaminated strawberry batches were analyzed by the ISO/TS15216-2 method indicating the presence of different amounts of RT-PCR inhibitors. A comparison of five different virus extraction methods using artificially contaminated strawberries containing high amounts of RT-PCR inhibitors revealed the best NoV RRs for the ISO/TS15216 method. Further improvement of NoV RRs from 2.83 ± 2.92% to 15.28 ± 9.73% was achieved by the additional use of Sephacryl(®)-based columns for RNA purification. Testing of 22 frozen strawberry samples from a batch involved in a gastroenteritis outbreak resulted in 5 vs. 13 NoV GI-positive and in 9 vs. 20 NoV GII-positive samples using the original ISO/TS15216 method vs. the extended protocol, respectively. It can be concluded that the inclusion of an additional RNA purification step can increase NoV detection by the ISO/TS15216-2 method in frozen berries containing high amounts of RT-PCR inhibitors.

Large multistate outbreak of norovirus gastroenteritis associated with frozen strawberries, Germany, 2012

Binary file ES_Abstracts_Final_ECDC.txt matches

New developments in safety testing of soft fruits

The chapter begins by establishing the definition of soft fruit, then discusses microbial and chemical hazards that might be found in soft fruit. Methods developed for virus detection in soft fruit are reviewed and, finally, the factors that mainly affect virus detection are detailed as these pathogens are currently linked to outbreaks caused by soft fruit consumption.

Detection and Typing of Norovirus from Frozen Strawberries Involved in a Large-Scale Gastroenteritis Outbreak in Germany

During September/October 2012, a norovirus gastroenteritis outbreak affecting about 11,000 people occurred in Germany. Epidemiological studies suggested that frozen strawberries represented the vehicle of infection. We describe here the analysis of frozen strawberries for the presence of norovirus. Samples were taken by applying a stratified subsampling scheme. Two different methods for virus extraction from strawberries were compared. First, viruses were eluted from strawberries under alkaline conditions and concentrated using a polyethylene glycol precipitation. Second, ultrafiltration was applied for concentration of viruses rinsed off of the berries. In both cases, RNA was extracted and analyzed by real-time RT-PCR. Application of the ultrafiltration method generally resulted in a lower detection rate. Noroviruses were detected in 7/11 samples derived from the lot of strawberries implicated in the outbreak using the precipitation method. Typing of norovirus revealed three different genotypes including a combination of norovirus genotype II.16 (viral polymerase) and II.13 (viral capsid). This genotype combination was also found in some of the patients that were involved in the outbreak, but that had not been reported in Germany so far. In conclusion, heterogeneously distributed noroviruses in frozen strawberries can be detected by applying an optimized combination of sampling procedures, virus extraction methods, and real-time RT-PCR protocols. The detection of several different genotypes in the strawberries may suggest contamination from sewage rather than from a single infected food handler.

Inactivation of enteric viruses in minimally processed berries and herbs

Several hepatitis A virus (HAV) and human norovirus (HuNoV) outbreaks due to consumption of contaminated berries and vegetables have recently been reported. Model experiments were performed to determine the effectiveness of freeze-drying, freeze-drying combined with heating, and steam blanching for inactivation of enteric viruses that might be present on the surface of berries and herbs. Inactivation of HAV and inactivation of feline calicivirus, a surrogate for HuNoV, were assessed by viral culturing and quantitative reverse transcription PCR (RT-PCR), whereas HuNoV survival was determined only by quantitative RT-PCR. While freeze-drying barely reduced (<1.3 log(10) units) the amount of HAV RNA detected in frozen produce, a greater decline in HAV infectivity was observed. The resistance of HuNoV genogroup I (GI) to freeze-drying was significantly higher than that of HuNoV GII on berries. Addition of a terminal dry heat treatment at 120 degrees C after freeze-drying enhanced virus inactivation by at least 2 log(10) units, except for HuNoV GII. The results suggest that steam blanching at 95 degrees C for 2.5 min effectively inactivated infectious enteric viruses if they were present in herbs. Our results provide data for adjusting food processing technologies if viral contamination of raw materials is suspected.

[Risk of infection in the home environment. Plea for a new risk assessment]

Within the last two decades risks posed by infectious diseases outside of hospitals and nursing homes had no high significance in the public perception. The home environment is regarded as a save shelter from infectious risks. In the mean time there have been dramatic socio-demographic, health policy and technological changes which have increased infectious risks outside medical facilities. In Germany up to 1.4 million people with multiple morbidities are nursed at home. Technological changes with the aim to protect the environment, like reduction of water temperature and water volumes in washing processes has lowered the efficacy to control pathogens. Thus it is time to revise the process of risk assessment in which not only aspects of environmental protection but also those of health protection must be taken into account. The article gives an overview of new risks and epidemiological changes and discusses the necessity of a new risk assessment and risk management approach which hopefully will lead to a changing paradigm.