Norovirus transfer between foods and food contact materials

Human infective noroviruses (NoVs) are a worldwide leading cause of foodborne illness and are frequently spread via infected food handlers preparing and manipulating food products such as deli sandwiches. The objective of the current study was to determine the efficiencies whereby NoV could be transferred between surfaces associated with the preparation of manually prepared foods such as deli sandwiches. Nonfood surfaces included gloves and stainless steel discs, and boiled ham, lettuce, and a sandwich bun were the ingredients of the deli sandwich. Both NoV GII.4 and the murine NoV 1 (MNV-1, a cultivable human NoV surrogate) were included in the presented study. Transfer of NoV GII.4 and MNV-1 between surfaces was performed by pressing an inoculated donor surface against an acceptor surface. To evaluate the effect of subsequent contact, donor surfaces were pressed a second time to an identical acceptor surface. Subsequently, NoV GII.4 and MNV-1 were detected using real-time reverse transcription PCR assays and plaque assays, respectively. Transfer of both viruses from gloves to stainless steel was inefficient, and virus transfer from food products to stainless steel occurred with more variability for NoV GII.4 than for MNV-1. Virus transfer from the stainless steel discs to the gloves was substantially more efficient than from the gloves to the stainless steel. NoV GII.4 and MNV-1 transfer from food products to the gloves occurred with varying efficiencies, although this variation was more evident for NoV GII.4. The MNV-1 inoculum was significantly less efficiently transferred to the acceptor surface at the second contact, which was not the case for NoV GII.4. The obtained transfer efficiency data may provide insights into the transfer of NoV during preparation of foods and can be included in risk assessment models describing the transmission of NoVs in this context.