Survival of murine norovirus and F-RNA coliphage MS2 on pork during storage and retail display

The existence of animal strains of norovirus (NV) that are closely related to human strains raises concerns about interspecies recombination and the potential for zoonotic transmission through undercooked meat products. Contamination of meat with NV can occur both via meat processing operations and poor food handler hygiene. There is a lack of knowledge on the survival of NV on raw meat because NV cannot be effectively cultivated and its detection is limited to molecular methods. The survival of murine norovirus (MNV) and MS2, as surrogates for NV, was determined on pork chops by plaque assay and real time RT-PCR. NV and MS2 displayed very high survival rates on vacuum packaged raw pork chops that were stored at 2 °C for up to 7 weeks and numbers declined little during subsequent retail display for 7 days. Maximum reductions for MNV and MS2 were 1.0 log PFU/cm2 and 0.6 log genome copies (GC)/cm2 or 1.1 log PFU/cm2 and 1.2 log GC/cm2, respectively. The viability of MS2 and MNV was not affected by the proteolytic enzymes present in the meat nor by numbers of bacteria that increased with time during storage in vacuum packs and while on retail display. MNV and MS2 can be considered as good surrogates for NV on raw meat. The findings of this study indicate that potentially pathogenic NV will likely survive extremely well on fresh meat and consumers could potentially be at risk when consuming undercooked meat that is contaminated with NV.