Assessment of the Impact on Human Health of the Presence of Norovirus in Bivalve Molluscs: What Data Do We Miss?

In the latest One Health ECDC EFSA technical report, Norovirus in fish and fishery products have been listed as the agent/food pair causing the highest number of strong-evidence outbreaks in the EU in 2019. This review aims to identify data gaps that must be filled in order to increase knowledge on Norovirus in bivalve molluscs, perform a risk assessment and rank the key mitigation strategies for this biological hazard, which is relevant to public health. Virologic determinations are not included in any of the food safety and process hygiene microbiologic criteria reflected in the current European regulations. In addition, the Escherichia coli-based indices of acceptable faecal contamination for primary production, as well as the food safety criteria, do not appear sufficient to indicate the extent of Norovirus contamination. The qualitative risk assessment data collected in this review suggests that bivalve molluscs present a high risk to human health for Norovirus only when consumed raw or when insufficiently cooked. On the contrary, the risk can be considered negligible when they are cooked at a high temperature, while information is still scarce for non-thermal treatments.

A new assay for quantitative detection of hepatitis A virus.

Hepatitis A virus (HAV) is mainly transmitted via contaminated food or water or through person-to-person contact. Here, we describe development and evaluation of a reverse transcription droplet digital PCR (RT-ddPCR) and reverse transcription real-time PCR (RT-qPCR) assay for detection of HAV in food and clinical specimens. The assay was evaluated by assessing limit of detection, precision, matrix effects, sensitivity and quantitative agreement. The 95 % limit of detection (LOD95 %) was 10 % higher for RT-ddPCR than for RT-qPCR. A Bayesian model was used to estimate precision on different target concentrations. From this, we found that RT-ddPCR had somewhat greater precision than RT-qPCR within runs and markedly greater precision between runs. By analysing serum from naturally infected persons and a naturally contaminated food sample, we found that the two methods agreed well in quantification and had comparable sensitivities. Tests with artificially contaminated food samples revealed that neither RT-ddPCR nor RT-qPCR was severely inhibited by presence of oysters, raspberries, blueberries or leafy-green vegetables. For this assay, we conclude that RT-qPCR should be considered if rapid, qualitative detection is the main interest and that RT-ddPCR should be considered if precise quantification is the main interest. The high precision of RT-ddPCR allows for detection of small changes in viral concentration over time, which has direct implications for both food control and clinical studies.

Specificity and application of a norovirus detection method based on receptor capturing / 中华实验和临床病毒学杂志

Objective@#To evaluate of the specificity of a new norovirus (NoV) detection method of in situ capture real-time quantitative reverse transcription polymerase chain reaction (ISC-RT-qPCR) and to apply the method for the detection of NoVs in fresh strawberry.@*Methods@#A panel of stool samples with different NoV genotypes and various inoculums were used for the experiments.@*Results@#We found that all the tested samples of eight genogroup Ⅱ (GⅡ) NoVs could be detected specifically by ISC-RT-qPCR. Moreover, in contrast to the conventional RT-qPCR method , the situation that the Ct value increased as the inoculum of NoV GⅡ decreased was not shown using ISC-RT-qPCR. When we tested NoVs in strawberry samples by ISC-RT-qPCR, the minimum test limit could reach 1.36 genocopy/10 g of fresh strawberry.@*Conclusions@#ISC-RT-qPCR is an effective and specific technic and it could be applied for the detection of infectious NoVs from stool samples and fresh strawberry samples.