Quantitative Trend Analysis of SARS-CoV-2 RNA in Municipal Wastewater Exemplified with Sewershed-Specific COVID-19 Clinical Case Counts

ABSTRACT

We demonstrate a new methodology for quantitative trend analysis (QTA) to analyze and interpret SARS-CoV-2 RNA wastewater surveillance results concurrently with clinical case data. This demonstration is based on the work completed under the Ontario (Canada) Wastewater Surveillance Initiative (WSI) by two laboratories in four wastewater treatment plants (WWTPs) at each of four large sewersheds, which were sampled over a 9-month period, along with sewershed-specific clinical case counts. The data from the last 5-months, representing a range of high and low case counts, was used for this demonstration. The QTA integrated clinical and wastewater virus signals, while combining recommendations from the United States Centers for Disease Control and Prevention (US CDC) and the Public Health Agency of Canada (PHAC). The key steps in the QTA consisted of signal normalization with pepper mild mottle virus (PMMoV), as a fecal biomarker, statistical linear break-point trend analysis and integration of both wastewater virus signal and clinical cases trend results. Using this approach, the wastewater virus and clinical cases trends, direction, and magnitude were clearly identified and provided a unified complementary tool to support public health decisions on a targeted, sewershed-specific basis.