Direct comparison of the persistence of infectious human norovirus and its cultivable surrogate, hepatitis A virus, on frozen raspberries

Émilie Larocque, Canadian Food Inspection Agency

Émilie Larocque1, Melissa Arango-Giraldo1, Marie-Josée Gagné2, Lisyanne Lamoureux2 and Julie Brassard2. 1.Canadian Food Inspection Agency, Food Virology National Reference Centre, Saint-Hyacinthe Laboratory, 3400 Casavant Boulevard West, Saint-Hyacinthe, QC J2S 8E3, Canada. 2.Agriculture and Agri-Food Canada, Saint-Hyacinthe Research and Development Centre, 3600 Casavant Boulevard West, Saint- Hyacinthe, QC J2S 8E3, Canada.

Food & Environmental Virology-I (Food)

Human noroviruses (HuNoV) cause around 1 million foodborne illnesses in Canada annually, with frozen berries being a common transmission vehicle. Historically, HuNoV persistence on food has been studied by molecular methods that detect viral RNA or by infectivity assays using cultivable surrogate viruses. Recently, a novel human intestinal enteroids (HIE) system has been shown to support HuNoV replication, allowing for the detection of infectious virus. This study aimed to evaluate the persistence of infectious HuNoV using the HIE system, and of HuNoV RNA on frozen raspberries. Additionally, it sought to compare this data with that of hepatitis A virus (HAV), a cultivable surrogate for HuNoV. Frozen raspberries were spiked with viruses and kept at -20 °C. Infectious virus and viral RNA were extracted from frozen raspberries over a twenty-one-day period. The infectious virus was evaluated in HIE by quantifying the fold increase in genome equivalents per well between 1 hour and 48 hours post-infection (hpi) using RT-qPCR. Viral RNA in the raspberry eluate was measured by RT-qPCR. After 21 days, no loss in HuNoV replication or RNA levels recovered from raspberries was observed. HAV also maintained its infectivity after 21 days. These results indicate that HuNoV can remain infectious on raspberries for at least 21 days at -20 °C, and the persistence kinetics of HuNoV and HAV is similar under these conditions. This information is valuable for improving risk assessment of HuNoV in frozen berries.