Temperature-dependent inactivation of human norovirus infectivity

Human norovirus is a leading cause of acute gastroenteritis and foodborne illness, with significant public health and economic impacts. Strategies to understand human norovirus persistence and inactivation in foods are essential to reduce risks. While there is emerging data on norovirus infectivity following intervention strategies such as heating, robust quantitative infectivity data remains limited. In this study, human intestinal enteroids (HIEs) were used to evaluate norovirus infectivity following heat treatments between 50 to 60 °C, for 1, 5, and 10 min. A capsid-viability assay using PMAxx™ with reverse transcription quantitative PCR (PMAxx-RT-qPCR) was also evaluated for its ability to distinguish infectious from non-infectious norovirus following exposure to 55, 63 and 90 °C. Using HIEs, an exponential rate of degradation of human norovirus at temperatures above 54 °C was observed. A 3-log 10 reduction in infectivity was observed at 60 °C after 1, 5, and 10 min of exposure with no significant difference between these times. No detectable reduction in norovirus infectivity at temperatures below 54 °C. In comparison, PMAxx-RT-qPCR data indicated an underestimation of heat-induced viral inactivation at ≥ 55 °C. This study provides evidence on heat-inactivation of human norovirus at temperatures relevant for food processing.