Detection of Norovirus and Hepatitis A Virus in Strawberry and Green Leafy Vegetables by Using RT-qPCR in Egypt

Concentration of foodborne viruses eluted from fresh and frozen produce: Applicability of ultrafiltration

Foodborne illnesses involving raw and minimally processed foods are often caused by human noroviruses (HuNoV) and hepatitis A virus (HAV). Since food is contaminated usually with small numbers of virions, these must be eluted from the food surface and then concentrated for detection. The objective of this study was to optimize an ultrafiltration (UF) concentration method for HAV and HuNoVs present on various fresh and frozen produce. The detection range of the optimized method and its applicability to different food matrices was compared to the reference method ISO 15216-1:2017. Strawberry, raspberry, blackberry, lettuce, and green onion (25 g) were contaminated with HAV, HuNoV GI.7 and HuNoV GII.4 and then recovered therefrom by elution. A commercial benchtop UF device was used for the concentration step. Viral RNA was extracted and detected by RT-qPCR. From fresh strawberries, recovery of HAV loaded at 104 genome copies per sample was 30 ± 13 %, elution time had no significant impact, and UF membrane with an 80-100 kDa cut-off in combination with Tris-glycine elution buffer at pH 9.5 was found optimal. At lower copy numbers on fresh strawberry, at least 1 log lower numbers of HuNoV were detectable by the UF method (103 vs 104 GII.4 copies/sample and 101 vs 103 GI.7 copies/sample), while HAV was detected at 101 genome copies/sample by both methods. Except on raspberry, the UF method was usually equivalent to the ISO method regardless of the virus tested. The UF method makes rapid viral concentration possible, while supporting the filtration of large volume of sample. With fewer steps and shorter analysis time than the ISO method, this method could be suitable for routine analysis of viruses throughout the food production and surveillance chain.

Meta-analysis of the prevalence of norovirus and hepatitis a virus in berries

Norovirus (NoV) and hepatitis A virus (HAV) stand as the predominant agents associated with viral foodborne infections. Outbreaks have been documented to be caused by various types of food items, including fresh and/or frozen berries. Comprehensive data concerning crucial viral pathogens in berries remain limited and are not currently available in aggregate form. Consequently, the present study aimed to compile the existing information regarding the prevalence of NoV and HAV in this matrix. Records of foodborne viruses were systematically extracted from database repositories up to December 2022, adhering to PRISMA standards and were subjected to a multilevel random effect meta-analysis model to determine the mean occurrence rate of NoV and HAV. A high heterogeneity across studies was observed (I2 = 82 %), reflecting variations in the prevalence of sampling locations, years, berry types, and sample conditions, among other potential contributing factors. The prevalence of NoV and HAV in berries was calculated at 2.12 % (95 % CI 1.74-2.59 %), and no statistically differences were observed among the viral types or genogroup categories. However, it is important to clarify that this estimate should be taken with caution given the high heterogeneity. There was no discernible correlation between viral prevalence and any particular berry type. However, there was a temporal correlation observed with the year of sampling, revealing a significantly decreasing trend throughout the study period. A significant influence of the sample condition (fresh or frozen) was observed in relation to the prevalence of NoV GII and HAV. Overall higher viral prevalences were identified in berries originating from African countries as compared to those sourced from other continents. It was also noted that the prevalence of NoV GI was significantly higher in samples collected directly from farms compared to those obtained from retailers. The outcomes of this comprehensive meta-analysis propose that while viral contamination of berries is diminishing in more recent times, the prevalence remains substantial in certain African countries, having a significant risk for foodborne infections. It is imperative to implement intervention strategies in these regions to enhance product safety.

A systematic review and meta-analysis indicates a high risk of human noroviruses contamination in vegetable worldwide, with GI being the predominant genogroup

Human noroviruses (HuNoVs) are the most predominant viral agents of acute gastroenteritis. Vegetables are important vehicles of HuNoVs transmission. This study aimed to assess the HuNoVs prevalence in vegetables. We searched the Web of Science, Excerpta Medica Database, PubMed, and Cochrane databases until June 1, 2023. A total of 27 studies were included for the meta-analysis. Statistical analysis was conducted using Stata 14.0 software. This analysis showed that the pooled HuNoVs prevalence in vegetables was 7 % (95 % confidence interval (CI): 3-13) worldwide. The continent with largest number of studies was Europe, and the highest number of samples was lettuce. As revealed by the results of the subgroup meta-analysis, the prevalence of GI genogroup was the highest (3 %, 95 % CI: 1-7). A higher prevalence was seen in vegetables from farms (18 %, 95 % CI: 5-37), while only 4 % (95 % CI: 1-8) in retail. The HuNoVs prevalence of ready-to-eat vegetables and non-ready-to-eat vegetables was 2 % (95 % CI: 0-8) and 9 % (95 % CI: 3-16), respectively. The prevalence by quantitative real time RT-PCR was 8 % (95 % CI: 3-15) compared to 3 % (95 % CI: 0-13) by conventional RT-PCR. Furthermore, the HuNoVs prevalence in vegetables was 6 % (95 % CI: 1-14) in ISO pretreatment method and 8 % (95 % CI: 1-19) in non-ISO method, respectively. This study is helpful in comprehensively understanding the prevalence of HuNoVs contamination in vegetables worldwide.

A review of nucleic acid-based detection methods for foodborne viruses: Sample pretreatment and detection techniques

Viruses are major pathogens that cause food poisoning when ingested via contaminated food and water. Therefore, the development of foodborne virus detection technologies that can be applied throughout the food distribution chain is essential for food safety. A common nucleic acid-based detection method is polymerase chain reaction (PCR), which has become the gold standard for monitoring food contamination by viruses due to its high sensitivity, and availability of commercial kits. However, PCR-based methods are labor intensive and time consuming, and are vulnerable to inhibitors that may be present in food samples. In addition, the methods are restricted with regard to site of analysis due to the requirement of expensive and large equipment for sophisticated temperature regulation and signal analysis procedures. To overcome these limitations, optical and electrical readout biosensors based on nucleic acid isothermal amplification technology and nanomaterials have emerged as alternatives for nucleic acid-based detection of foodborne viruses. Biosensors are promising portable detection tools owing to their easy integration into compact platforms and ability to be operated on-site. However, the complexity of food components necessitates the inclusion of tedious preprocessing steps, and the lack of stability studies on residual food components further restricts the practical application of biosensors as a universal detection method. Here, we summarize the latest advances in nucleic acid-based strategies for the detection of foodborne viruses, including PCR-based and isothermal amplification-based methods, gene amplification-free methods, as well as food pretreatment methods. The principles, strengths/disadvantages, and performance of each method, problems to be solved, and future prospects for the development of a universal detection method are discussed.

Detection of Hepatitis A RNA, Hepatitis E RNA, Human Adenovirus F DNA, and Norovirus RNA in Fresh and Frozen Berry Products at Point of Retail in Ireland

Soft fruits are at particular risk of contamination with enteric viruses such as Hepatitis A virus (HAV), Hepatitis E Virus (HEV), Norovirus (NoV), Human Adenovirus (HAdV) and Sapovirus (SaV). The aim of this study was to investigate, for the first time, the presence of these biological agents in ready to eat (RTE) berries at point of retail in Ireland. A sampling strategy was designed in which RTE fresh and frozen strawberries and raspberries were purchased from five retailers between May and October 2018. Reverse Transcriptase Polymerase Chain Reaction (RT-qPCR) assays for HEV RNA, Nov RNA, SaV RNA, and human Adenovirus species F DNA (HAdV-F) were performed on 239 samples (25g portions). Viral nucleic acid was present in 6.7% (n = 16) of samples tested as follows: HAV RNA (n = 5), HAdV-F DNA (n = 5), HEV RNA (n = 3) and NoV GII RNA (n = 3). Sapovirus RNA was not detected in any product. No significant differences were found between berry type, fresh/frozen status, or supermarket source. This study suggests a risk that exists across all retail outlets however only low levels of nucleic acid ranging from 0 to 16 genome copies/g were present. Although these findings may reflect non-viable/non-infectious virus the continued provision of risk mitigation advice to consumers is warranted and further work is required to ensure control measures to reduce contamination are implemented and enforced.

Prevalence of enteric viruses in wastewater in Egypt after the COVID-19 pandemic

People's hygienic habits greatly affect the spreading rate of enteric viruses. After the COVID-19 pandemic, many people followed announced precautions and improved their hygienic status to protect themselves from SARS-CoV-2 infection. Here, we studied if this indirectly affected the prevalence of enteric viruses in Egypt. A total of 21 samples (one sample per week) were collected from the Zenin wastewater treatment plant (WWTP) through the period between August 2021 and March 2022. Detection of adenovirus, hepatitis A virus (HAV), and rotavirus showed their presence in 66, 14.3, and 9.5% of the collected samples, respectively. Comparing those percentages to previously published data concerned with the detection of the same viruses from the same WWTP or others revealed a remarkable decrease in the prevalence of the three viruses after the COVID-19 pandemic. This allows the conclusion that safety precautions against SARS-CoV-2 lead indirectly to a reduction of adenovirus, HAV, and rotavirus prevalence rates.