Wastewater-based surveillance for seasonal respiratory viruses provides a one-week lead to clinical cases and hospital admissions.

Wastewater-based surveillance (WBS) is a complementary tool for infectious disease surveillance, providing independent data that is inclusive of entire populations. We evaluated the role of WBS in tracking seasonal respiratory viral infections caused by influenza A (IAV) and B (IBV), and respiratory syncytial virus (RSV) - pathogens responsible for significant morbidity and mortality and imposing substantial burdens on healthcare systems. Longitudinal surveillance was performed 1-3 times weekly from January 2022-June 2024, encompassing multiple respiratory virus seasons, across the three municipal wastewater treatment plants serving Calgary, Canada's fourth largest city. Flow-normalized viral loads (gene copies/day) of IAV, IBV and RSV in 24-h composite wastewater were analyzed and compared to confirmed cases leveraging metadata from the single provincial health authority - Alberta Health Services. IAV and RSV RNA in wastewater peaked in winter months (November to February), with maximum viral loads of 4.4 × 1013 and 7.9 × 1013 (gene copies/day), respectively. In contrast, IBV was generally observed in late winter/early spring with low and infrequent periods of activity. Wastewater signals for all three respiratory viruses strongly correlated with clinical metrics including laboratory-confirmed cases, test percent positivity, and respiratory virus-associated hospital admissions (Spearman r value range: 0.66-0.90). Notably, WBS provided a 1-week lead time relative to traditional clinical respiratory viral surveillance indicators. WBS is a versatile technology that provides objective information that can augment traditional case-based surveillance of respiratory viruses and be used to predict changing disease prevalence and health resource requirements across communities.