Norovirus (NoV) and hepatitis A virus (HAV) are the most important foodborne viruses. Fresh produce has been identified as an important vehicle for their transmission. In order to supply a basis to identify possible prevention and control strategies, this review intends to demonstrate the fate of foodborne viruses in the farm to fork chain of fresh produce, which include the introduction routes (contamination sources), the viral survival abilities at different stages, and the reactions of foodborne viruses towards the treatments used in food processing of fresh produce. In general, the preharvest contamination comes mainly from soli fertilizer or irrigation water, while the harvest and postharvest contaminations come mainly from food handlers, which can be both symptomatic and asymptomatic. Foodborne viruses show high stabilities in all the stages of fresh produce production and processing. Low-temperature storage and other currently used preservation techniques, as well as washing by water have shown limited added value for reducing the virus load on fresh produce. Chemical sanitizers, although with limitations, are strongly recommended to be applied in the wash water in order to minimize cross-contamination. Alternatively, radiation strategies have shown promising inactivating effects on foodborne viruses. For high-pressure processing and thermal treatment, efforts have to be made on setting up treatment parameters to induce sufficient viral inactivation within a food matrix and to protect the sensory and nutritional qualities of fresh produce to the largest extent.

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This study intends to establish and apply methods evaluating both viral capsid and genome integrities of human noroviruses (NoVs), which thus far remain nonculturable. Murine norovirus 1 (MNV-1) and human NoV GII.4 in phosphate-buffered saline suspensions were treated with heat, UV light, or ethanol and detected by reverse transcription-quantitative PCR (RT-qPCR), long-range RT-qPCR, binding RT-qPCR, and binding long-range RT-qPCR. For MNV-1 heated at 60°C for 2 and 30 min, limited reductions of genomic copies (<0.3-log) were obtained by RT-qPCR and long-range RT-qPCR, while the cell-binding pretreatments obtained higher reductions (>1.89-log reduction after 60°C for 30 min by binding long-range RT-qPCR). The human NoV GII.4 was found to be more heat resistant than MNV-1. N oroviruses (NoVs) are a group of important food-borne viruses and the leading cause of human gastroenteritis worldwide (1, 2). Methods for the detection of NoVs have been progressing over a number of years. Due to the inability to culture NoVs in vitro (3, 4), reverse transcription-quantitative PCR (RTqPCR) is still recognized as the gold standard for virus detection, although this method cannot differentiate between infectious and noninfectious viruses (5, 6). Thus far, prediction of NoV infectivity has been attempted from the integrities and/or functions of viral RNA molecules and capsid proteins (5), which are the two essential parts for an intact and infectious virus particle.As for the genome integrity evaluation, although it is possible to amplify nearly full-length human NoV genomes (7), the amplification efficiency decreases with fragment size, thus making amplification of full-length genomic RNA relatively insensitive. Wolf et al. (8) suggested that one important factor for assessing the genomic integrities of RNA viruses is the dependency of the reverse transcription (RT) reaction on high-quality, nonfragmented template RNA. This fact can be exploited by separating the PCR amplification site and RT priming site within the virus genome. This approach has been used to examine the integrity of the human NoV genome after high-temperature (72°C) and UV treatment (8).Multiple studies have been conducted to assess the number of infectious NoVs based on the capsid integrity or function (9-11). Recently, binding-based RT-PCRs were developed in our laboratory and were able to decrease the detection of noninfectious NoVs by approximately 1 to 3 log, whereas all infectious viral particles were detected (12). For murine norovirus 1 (MNV-1), the cell line RAW 264.7 and the ganglioside GD1a were used as binding receptors and, for human NoVs, differentiated Caco-2 cells and pig gastric mucin were tested as the binding receptors (12).Our aim here was to apply these methods (RT-qPCR, longrange RT-qPCR, and binding RT-qPCR) and the combination method (binding long-range RT-qPCR) in order to indicate the viral integrities of NoVs. First, murine norovirus 1 (MNV-1, a surrogate of human NoVs) and human NoV GII.4 were treated in phosphate-buffered salin...

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Risk assessments related to use of water and safety of fresh produce originate from both water and food microbiology studies. Although the set-up and methodology of risk assessment in these 2 disciplines may differ, analysis of the current literature reveals some common outcomes. Most of these studies from the water perspective focus on enteric virus risks, largely because of their anticipated high concentrations in untreated wastewater and their resistance to common wastewater treatments. Risk assessment studies from the food perspective, instead, focus mainly on bacterial pathogens such as Salmonella and pathogenic Escherichia coli. Few site-specific data points were available for most of these microbial risk assessments, meaning that many assumptions were necessary, which are repeated in many studies. Specific parameters lacking hard data included rates of pathogen transfer from irrigation water to crops, pathogen penetration, and survival in or on food crops. Data on these factors have been investigated over the last decade and this should improve the reliability of future microbial risk estimates. However, the sheer number of different foodstuffs and pathogens, combined with water sources and irrigation practices, means that developing risk models that can span the breadth of fresh produce safety will be a considerable challenge. The new approach using microbial risk assessment is objective and evidence-based and leads to more flexibility and enables more tailored risk management practices and guidelines. Drawbacks are, however, capacity and knowledge to perform the microbial risk assessment and the need for data and preferably data of the specific region.Keywords: fruits and vegetables, health risk, mitigation strategies, quantitative microbial risk assessment, water Practical Application: This manuscripts intends to give an extensive overview of approaches and challenges of past and future quantitative microbial risk assessment studies in the fresh produce chain related to the use of water in order to aid further research efforts in this area.