No Clinical Symptom Experienced after Consumption of Berry Fruits with Positive RT-qPCR Signals of Human Norovirus.

Mohamad Eshaghi Gorji,Dan Li,Mitchie Y Zhao,Malcolm Turk Hsern Tan

doi:10.3390/pathogens10070846

Abstract

Human noroviruses (hNoVs) are the most important foodborne viruses, and soft berries are one of the most common food sources of hNoV outbreaks and contamination. This paper presents a human volunteer study in order to investigate the correlation between molecular detection results of hNoV in berries with the public health risks. The participants with diverse histo-blood group antigens (HBGAs) phenotypes were required to consume self-purchased berries and meanwhile submit aliquots of the products for reverse transcription-quantitative polymerase chain reaction (RT-qPCR) detection. As a result, none of the 20 participants reported any hNoV infection-like symptoms after six independent consumptions (120 consumptions in total). In contrast, within the 68 berry samples with >1% virus recoveries, 28 samples were detected to be positive for hNoV GI and/or GII (the positive rate at 41%). All of the positive signals were below the limit of quantification (<120 genome copies/g) except one fresh strawberry sample at 252 genome copies/g. It is expected that this study would contribute to the definition of quantitative standards for risk assessment purposes in the future.

Highlights

Human noroviruses cause between 73% to greater than 95% of global epidemic non-bacterial gastroenteritis outbreaks and approximately half of all gastroenteritis outbreaks [1]
The detection of Human noroviruses (hNoVs) from food samples still relies on molecular techniques, mostly reverse transcription-quantitative polymerase chain reaction (RT-qPCR)
Due to the technical limitations, clinical trials are currently the only possibility validating the direct public health risks of the food samples detected with hNoV positive signals by RT-qPCR

Summary

Introduction

Human noroviruses (hNoVs) cause between 73% to greater than 95% of global epidemic non-bacterial gastroenteritis outbreaks and approximately half of all gastroenteritis outbreaks [1]. Fresh produce, especially soft berries, are one of the most common food sources of hNoV outbreaks and contamination events, as reviewed by Bozkurt et al [2]. RT-qPCR, which is recognized as the gold standard for hNoV detection and proposed in the ISO/TS 15216 methods, cannot differentiate between infectious and non-infectious viruses. Still there is a need for correlation of presence and levels of hNoV as detected by RT-qPCR in foods such as berries to the actual public health risks. In order to evaluate the hNoV contamination in berry products at the retail markets and the actual public health risks, a human volunteer study was conducted, and the participants were required to consume self-purchased berries and to submit aliquots of the products for RT-qPCR detection

Results and Discussion

Human Volunteer Study Organization

Virus Extraction Procedures from Berry Samples Based on ISO 15216-2

Virus Extraction from Stool Samples

RNA Extraction and RT-qPCR Analyses