Microgreen Variety Impacts Leaf Surface Persistence of a Human Norovirus Surrogate

Human norovirus (HuNoV) is a pathogenic agent that is frequently associated with foodborne disease outbreaks linked to fresh produce. Within microgreen production systems, understanding of virus transmission routes and persistence is limited. To investigate virus persistence on microgreen leaf surfaces, this study mimicked virus contaminations caused during microgreen handling by farm workers or during overhead irrigation with contaminated water. Specifically, approximately 5 log PFU of Tulane virus (TV)-a HuNoV surrogate-was inoculated on sunflower (SF) and pea shoot (PS) microgreen leaves at 7-day age. The virus reduction on SF was significantly higher than PS (p < 0.05). On day 10, total TV reduction for SF and PS were 3.70 ± 0.10 and 2.52 ± 0.30 log PFU/plant, respectively. Under the environmental scanning electron microscope (ESEM) observation, the leaf surfaces of SF were visually smoother than PS, while their specific effect on virus persistence were not further characterized. Overall, this study revealed that TV persistence on microgreen leaves was plant variety dependent. In addition, this study provided a preliminary estimation on the risk of HuNoV contamination in a microgreen production system which will aim the future development of prevention and control measures.