Tracking SARS-CoV-2 transmission: evaluation of the Québec wastewater surveillance program

Québec's COVID-19 wastewater surveillance program, initiated in March 2022, was evaluated after its first year to determine its effectiveness in tracking SARS-CoV-2 transmission. The evaluation assessed the program's validity, completeness, and timeliness. As per visual analysis, results showed temporal coherence between wastewater and clinical data, although this was period dependent. Cross-correlation function analysis failed to generate consistent results and interpretable patterns between wastewater signal and clinical indicators. The percentage of unplanned missing wastewater results was minimal (ranging from 1% to 21%, with a median of 3%). Planned missing data caused by different sampling regimen required adaptation in data processing and interpretation. The median time between infection and wastewater data availability was 13.1 days, compared to 8 days for clinical data, although high variability in delays was seen between sampling sites. The wastewater data dissemination delay was the main bottleneck to provide timely information to public health authorities. This initial evaluation highlights the program's potential to generate complementary information to clinical data and can help future studies navigate the complexities of wastewater monitoring.