Evaluation of the Public Health Utility of Wastewater-based Surveillance for Monitoring SARS-CoV-2 in Scotland

About this release

Public Health Scotland (PHS), in partnership with Biomathematics and Statistics Scotland (BioSS) and the University of Edinburgh (UoE), undertook an evaluation to formally assess the public health utility of wastewater-based surveillance of SARS-CoV-2 in Scotland.

The report describes the approach, findings and conclusion, most notably that the Wastewater Monitoring Programme in Scotland has value in supporting three key epidemiological goals: (i) the description of broad temporal trends and geographic spread of COVID-19, (ii) the timely identification of new COVID-19 growth periods, and (iii) determination of predominant SARS-CoV-2 variants. It is therefore recommended that COVID-19 wastewater monitoring activities continue, with periodic review to ensure they address the evolving public health need for COVID-19 and wider infectious respiratory disease surveillance. Caution is required, however, in the application of the system for informing immediate public health action, particularly when applied to smaller geographic areas. A number of recommendations are made for future improvements to ensure the reliability and validity of the system in Scotland.

Main points

• The quality of intelligence generated by the system for monitoring trends in COVID-19 activity, and presence of SARS-CoV-2 variants, is dependent on the specific variants in circulation, and with variation in performance across locations.
• The value of the system is in trend analysis, and potentially in informing predictive and scenario modelling exercises. Owing to the fluctuating nature of the data, caution is needed in interpreting the outputs without statistical smoothing techniques, and in using the outputs to inform immediate public health action.

Background

In June 2020, a national Wastewater Monitoring Programme for COVID-19 was established in Scotland. The system was established to support the emergency COVID-19 pandemic response. At the time, the programme was found to have successfully monitored SARS-CoV-2 trends and informed modelling exercises to understand the spread and potential impact of COVID-19 in Scotland. There is now a need to reassess whether the system is effectively supporting the current public health needs of Scotland.

While the World Health Organization provide guidance on emerging best practices for wastewater surveillance, specific recommendations are not made owing to evolving methods and possible differences in performance or local needs. In Scotland, a change in the performance of the data has been observed since the introduction of the SARS-CoV-2 Omicron variant and there are known geographic variations in performance.

In view of the need for improved understanding, Public Health Scotland (PHS), in partnership with Biomathematics and Statistics Scotland (BioSS) and the University of Edinburgh (UoE), undertook an evaluation to formally assess the public health utility of wastewater-based surveillance of SARS-CoV-2 in Scotland.

The report describes the approach, findings and conclusion, most notably that the Wastewater Monitoring Programme in Scotland has value in supporting three key epidemiological goals: (i) the description of broad temporal trends and geographic spread of COVID-19, (ii) the timely identification of new COVID-19 growth periods, and (iii) determination of predominant SARS-CoV-2 variants. It is therefore recommended that COVID-19 wastewater monitoring activities continue, with periodic review to ensure they address the evolving public health need for COVID-19 and wider infectious respiratory disease surveillance. Caution is required, however, in the application of the system for informing immediate public health action, particularly when applied to smaller geographic areas. A number of recommendations are made for future improvements to ensure the reliability and validity of the system in Scotland.