Impact of COVID-19 Nonpharmaceutical Interventions on the Extent of Norovirus Contamination in Oyster Production Areas in Ireland during Winter 2020 to 2021

• Published in: Journal of food protection 2022-10, Vol.85 (10), p.1397-1403
• Main Authors: Keaveney, Sinéad, Rupnik, Agnieszka, Fitzpatrick, Amy, Devilly, Leon, Fahy, James, Doré, Bill
• Format: Article
• Language: English
• Subjects: Animals; Bivalve shellfish; Contamination; Coronaviruses; COVID-19; Disease transmission; Efficiency; Food safety; Genomes; Genotype; Human wastes; Humans; Ireland; Laboratories; Norovirus; Ostreidae; Oysters; Pandemics; Process controls; Public health; Reverse transcription quantitative PCR; SARS-CoV-2; Seasons; Severe acute respiratory syndrome coronavirus 2; Shellfish; Statistical analysis; Surveillance; Viral contamination; Viral diseases; Viruses; Wastewater; Wastewater discharges; Winter
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/JFP-22-031

A significant decrease in norovirus prevalence and concentration was observed in oyster production areas in Ireland during winter 2020 to 2021. Oyster production areas impacted by human wastewater discharges that had been undergoing norovirus surveillance since 2018 were investigated. Samples collected in the winter seasons of 2018 to 2019 and 2019 to 2020, prior to when the COVID-19 pandemic interventions were applied, showed a prevalence of 94.3 and 96.6%, respectively, and geometric mean concentrations of 533 and 323 genome copies per g, respectively. These values decreased significantly during the winter of 2020 to 2021 (prevalence of 63.2% and geometric concentration of below the limit of quantification), coinciding with the control measures to mitigate the transmission of severe acute respiratory syndrome coronavirus 2 of the genus Betacoronavirus. Divergence between norovirus GI and GII prevalence and concentrations was observed over the 3-year monitoring period. Norovirus GII was the dominant genogroup detected in winter 2020 to 2021, with over half of samples positive, although concentrations detected were significantly lower than prepandemic winters, with a geometric mean concentration of below the limit of quantification. •Oyster surveillance revealed the norovirus rate during the COVID-19 pandemic.•SARS-CoV-2 mitigation measures had an indirect impact on norovirus transmission.•A decrease in norovirus levels was seen in 2020 to 2021 compared with prepandemic winters.•Norovirus concentrations were significantly lower than in previous winter periods.