Project Number: 1935-42000-065-08
Start Date: Jun 01, 2014
End Date: May 31, 2019
Major data gaps in the quantitative risk assessment include the absence of data on the fraction of norovirus particles that are infectious at each stage of the process model and the impact of biological and mitigation/control steps on the ratio of infectious to total norovirus particles. Detection methods for norovirus are based on molecular methods that cannot distinguish between infectious and non-infectious particles Currently the draft quantitative risk assessment model uses viral surrogate data, where available, to evaluate the impact of a given process on the infectious particle concentration. However, such data rarely include complementary molecular measurements that would inform changes in the infectious to total particle ratio. This latter information is needed to link molecularly-based measurements of norovirus to public health metrics. The research supported by the interagency agreement will serve to fill these data gaps by providing a suite of measurements of norovirus and critical viral surrogates before and after environmental or mitigation/control steps that include (1) Quantitative measures of the number of norovirus particles present, the numbers of norovirus particles that bind porcine gastric mucin, and the numbers of particles that do not bind porcine gastric mucin. The ability of a norovirus particle to bind porcine gastric mucin is a surrogate measure of the potential of the particle to be infective. (2) Quantitative measures of the number of Male Specific MS2 (phage MS2) particles by qRT-PCR and conventional culture techniques. (3) Quantitative measures of Murine Norovirus or other appropriate norovirus surrogate by qRT-PCR and conventional culture techniques. Together, these measurements will enable FDA to more accurately describe norovirus survival in the environmental and in food and as a result, provide more accurate measures of the risk reduction provided by different risk mitigation/control steps.