Hydrogen Peroxide Vapour Treatment Inactivates Norovirus But Has Limited Effect On Post-Treatment Viral Rna Levels

Background: Hydrogen peroxide vapour is used as a room disinfectant. Its activity against murine norovirus, a surrogate viability marker for human norovirus, indicates that it is also active against human norovirus. Aim: The aim of this study is to assess how this effect on viability is reflected in measurements of RNA by quantitative PCR (qPCR). Methods: Faeces suspensions of two human norovirus field strains, genogroup I and II and one cultured murine norovirus strain, (genogroup V) were dried on plastic plates, and underwent hydrogen peroxide vapour treatment or were mock treated. The influence of hydrogen peroxide on RNA was measured on genogroups I, II and V by qPCRs and for the cultivable murine norovirus also for viability by cell culture. Virucidal activity on murine norovirus was measured by endpoint titrations as the 50% tissue culture infectious dose, based both on cytopathic effect and on presence of replicating intracellular minus strand RNA. Results: The mean impact on the human norovirus qPCRs was 0.4 log(10). The murine norovirus qPCR changed by 1.7 log(10) but by an alternative qPCR only by 0.4 log(10). These minor changes contrasted the 4.5-5.0 log(10) murine norovirus viability reduction after treatment measured by cytopathic effect or intracellular negative-strand RNA. Conclusion: Inactivation of murine norovirus viability by hydrogen peroxide vapour was not reflected in qPCR levels. This finding might be extrapolated to the related human norovirus genogroups. We further found that cellular minus strand murine norovirus PCR was an observer-independent marker to study reduction of murine norovirus viability.