Scotland introduced a Wastewater-based monitoring system in summer 2020 with samples taken at Wastewater Treatment Works (WWTW) by Scottish Water (SW). These were then analysed by the Scottish Environmental Protection Agency (SEPA) using qPCR to quantify levels of COVID-19 RNA.

From December 2020 until March 2024, BioSS was funded by the Scottish Government to statistically analyse and visualise the data, in terms of what wastewater has to say about COVID-19 prevalence. This was a complex task as the measured levels demonstrated a significant degree of variability. In addition, the wastewater COVID-19 levels do not only depend on the number of COVID-19 cases at the time but are influenced by a series of other factors, including the amount of water going through a WWTW on the sampling day, the population covered by the catchment area, as well as lab-specific factors. By early 2021, more than 100 WWTWs were regularly sampled, covering 80% of the Scottish population.

The role of BioSS

BioSS developed an analysis pipeline for this purpose that allowed us to report the latest findings to the Scottish Government and other stakeholders on a weekly basis. Parts of these reports were made available to the general public every other week as part of the Scottish Government’s research findings, which can be found on the Scottish Government website. Our reports also fed into regular reports issued by Public Health Scotland and were used to estimate the reproductive number R by Scottish Government modellers. At the stage of the pandemic where population-wide testing was no longer happening and the Office of National Statistics Coronavirus Infection Survey was published with some delay, the COVID-19 levels in wastewater were the most up-to-date data resource to assess the state of the pandemic across Scotland.

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Example maps showing COVID-19 RNA levels across Scotland from wastewater analysis.