Environmental sampling for detection of norovirus using a real-time RT-PCR Assay: A Tool for Foodborne Outbreak Investigations

This project was designed to develop a method for the collection of environmental samples during prolonged Norovirus (NoV) outbreak investigations, and to develop real-time RT-PCR assays to analyze environmental samples for GI and GII noroviruses. The collection and processing of environmental samples could provide epidemiological data to facilitate investigations of prolonged NoV outbreaks and could guide public health NoV intervention strategies. Real-time RT-PCR assays for the detection of GI and GII NoVs were developed by adapting the State Hygienic Laboratory clinical GI and GII assays to the AB 7500 Fast platform. Analysis of the GI assay performance yielded a dilution curve slope = 3.28, R2 = 0.999 and a calculated amplification efficiency of 102%. The GII assay yielded a dilution curve slope = 3.39, R2 = 0.999 and a calculated amplification efficiency of 97%. Amplification efficiencies determine the sensitivity and the limit of detection of real-time RT-PCR assays. Optimum efficiencies range from 95%-105%, with a 100% efficiency indicating exponential amplification of targeted nucleic acid.

To develop a method for the collection of environmental samples, multiple swab types were tested to determine their ability to recover NoV from laboratory spiked environmental surfaces. It was determined that foam swabs moistened with viral transport media were most effective in recovering NoV from spiked surfaces. A field test of the environmental sampling method was conducted by sampling environmental surfaces in four restaurants in one Iowa community. NoVs were not detected in the environmental samples. The collection and processing of environmental samples when conducting an investigation of a prolonged NoV outbreak could provide additional information on the epidemiology of NoV transmission and infection.