Multi-tiered strategy for large-scale wastewater detection of SARS-CoV-2 in low-case settings provides confidence for public health actions.

Wastewater surveillance has played a pivotal role in monitoring SARS-CoV-2 transmission worldwide. However, developing and implementing the methods underpinning these programmes in regions with prolonged periods of low community transmission has proven challenging. In Victoria, Australia, wastewater surveillance provided early warning of unknown community infections and informed timely public health decisions to limit their spread when case numbers were low. To achieve this, we developed a methodological approach sensitive to extremely low viral loads and could readily identify false positives within short turnaround times. Here, we describe the successful development, implementation, and evaluation of analytic methods using Reverse Transcriptase Quantitative Polymerase Chain Reaction (RT-qPCR) and amplicon sequencing in tandem with CRISPR DETECTR in an ongoing, large-scale surveillance programme to detect SARS-CoV-2 in wastewater in Victoria, Australia. Our study covers ten months, from July 2020 to April 2021, and includes all state-wide health districts and prolonged periods with no known, active community cases among the ∼6.7 million population.