Purpose: To test the efficacy of a novel surface sampling material (“wipes”) relative to human NoV recovery.
Methods: Dilutions of a representative human NoV GII.4 outbreak strain were applied to frequently used hard surfaces (stainless steel and ceramic) and the surface of representative foods (green pepper, apple, tomato, and cheese). After inoculum drying, the sampler was used to recover viruses by wiping the surface in a circular, back and forth motion. The wipes were then directly processed for nucleic acid extraction using the automated EasyMag system, and the viral RNA quantified by RT-qPCR targeting the orf 1-orf 2 junction. The efficiency of recovery of virus by the wipes was determined by direct comparison of RT-qPCR signals to a standard curve produced from the NoV GII.4 inoculum.
Results: Recovery efficiency of the wipes ranged from 37-100% when used for sampling fresh fruits, vegetables, and hard surfaces artificially inoculated with high concentrations (3.4-5.4 log genome equivalent copies, GEC) of GII.4 human NoV. At lower inoculum concentrations (1.4-2.4 log GEC), the wipes also yielded positive RT-qPCR signals for NoV. Less efficient recovery was observed for cheese, ranging from 18-52% at high inoculum concentration, and failure to detect the GII.4 strain at lower concentrations.
Significance: The wipes are a user-friendly means by which to sample hard surfaces and foods that also provide high recovery efficiency for human NoV. They are being field tested in environmental surveys designed to evaluate NoV prevalence in public restrooms during the typical epidemic (winter) season.