Potential future implications of the COVID-19 pandemic on Norovirus infections in England
Authors: M. Hotham
Journal: Journal of Infection (2021)

I read with interest the recent article by Eigner et al., in the Journal of infection, highlighting the reduction in Norovirus (NoV) infections reported in Germany since the introduction of COVID-19 containment measures in 20201Eigner U. Verstraeten T. Weil J. Decrease in norovirus infections in Germany following COVID-19 containment measures.J Infect. 2021; https://doi.org/10.1016/j.jinf.2021.02.012Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar. In the UK, there has been a reduction in both NoV infections and outbreaks reported to Public Health England (PHE) since the introduction of Nonpharmaceutical Interventions (NPIs) by the UK government to contain the COVID-19 pandemic in March 20202Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. The GII.4 NoV strain was detected in the mid-20th century and has undergone evolution in the form of 7 new variants since the 1990s which have been associated with global epidemics3Robilotti E. Deresinski S. Pinsky B Norovirus.Clin. Microbiol. Rev. 2015; 28: 134-164https://doi.org/10.1128/CMR.00075-14Crossref PubMed Scopus (427) Google Scholar. These have appeared on average every 2–3 years, but a new variant has not been detected since 'The Sydney strain' in 20123Robilotti E. Deresinski S. Pinsky B Norovirus.Clin. Microbiol. Rev. 2015; 28: 134-164https://doi.org/10.1128/CMR.00075-14Crossref PubMed Scopus (427) Google Scholar. There are concerns about the potential for an undetected new strain shift, as a result of the reduced surveillance over the last year4Douglas A. Sandmann F. Allen D. Celma C. Beard S. Larkin L. Impact of COVID-19 on national surveillance of norovirus in England and potential risk of increased disease activity in 2021.J Hospital Infect. 2021; https://doi.org/10.1016/j.jhin.2021.03.006Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar. PHE surveillance data on NoV is collected via four main sources2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. The Second-Generation Surveillance System (SGSS) records all positive norovirus tests reported to labs in England2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. The Hospital Norovirus Outbreak Reporting System (HNORS) includes online reporting of both confirmed and suspected hospital outbreaks of norovirus across England2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. HPZone is used by Health Protection Teams (HPTs) to record suspected and confirmed enteric virus (EV) outbreaks notified to them2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. The Enteric Virus Unit monitors genotype and characterisation of NoV nationally2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. Data is collected across the 'Norovirus season' which runs from week 27 (July) in year 1 to week 26 (June) in year 2, in order to capture the winter peak of activity2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. PHE surveillance data since week 12 of the 2019/2020 season through to the 2020/2021 season have shown markedly reduced levels of norovirus positive tests and EV outbreaks reported compared with the 5-season average2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. The cumulative total of EV reports in the 2020/2021 season to week 7 is 89% lower than the 5-season average2Public Health England. National Norovirus and Rotavirus Bulletin Routine norovirus and rotavirus surveillance in England, 2020 to 2021 season Week 11 report: data to week 9 (7 March 2021). Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/966403/Norovirus_bulletin_2020-2021_week-09.pdf (last accessed April 2021)Google Scholar. It is hard to argue that the NPIs introduced to contain COVID-19 have not had a significant impact on the transmission of NoV. However, this must be interpretated with caution. The underreporting of enteric virus cases is an issue that will only have worsened during the pandemic, due to factors such as reduced access to NHS services and the impact on testing capacity4Douglas A. Sandmann F. Allen D. Celma C. Beard S. Larkin L. Impact of COVID-19 on national surveillance of norovirus in England and potential risk of increased disease activity in 2021.J Hospital Infect. 2021; https://doi.org/10.1016/j.jhin.2021.03.006Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar. Douglas et al., discussed the reduction in the referral of NoV-positive samples in the UK for characterisation and genotyping during the pandemic in the Journal of hospital infection4Douglas A. Sandmann F. Allen D. Celma C. Beard S. Larkin L. Impact of COVID-19 on national surveillance of norovirus in England and potential risk of increased disease activity in 2021.J Hospital Infect. 2021; https://doi.org/10.1016/j.jhin.2021.03.006Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar. They suggest that such a significant reduction could result in key indicators for NoV strain replacement events being missed4Douglas A. Sandmann F. Allen D. Celma C. Beard S. Larkin L. Impact of COVID-19 on national surveillance of norovirus in England and potential risk of increased disease activity in 2021.J Hospital Infect. 2021; https://doi.org/10.1016/j.jhin.2021.03.006Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar. With UK COVID containment measures set to ease, the authors warn of the ongoing risk to healthcare services due to the potential occurrence of a new NoV strain in a population with low levels of immunity4Douglas A. Sandmann F. Allen D. Celma C. Beard S. Larkin L. Impact of COVID-19 on national surveillance of norovirus in England and potential risk of increased disease activity in 2021.J Hospital Infect. 2021; https://doi.org/10.1016/j.jhin.2021.03.006Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar. There have been reports of increasing numbers of NoV outbreaks across China since the easing of COVID-19 restrictions there. This highlights the reality of the risk of significant NoV outbreaks occurring to a greater degree once containment measures are lifted. It is clear to see that, despite factors leading to underreporting of surveillance data, there has been a substantial impact on NoV infections due to COVID-19 containment measures implemented both in the UK and globally. What is not clear is what the implications of this may be for the future. There remains the possibility for the emergence of new NoV strains with epidemic potential as measures are lifted in the short term. Whether the significant societal and behavioural changes that have occurred during the pandemic will lead to a reduction in transmission of infectious diseases, such as influenza and norovirus, remains to be seen. None to declare.