Infectious Disease
Evaluating Wastewater Surveillance for COVID-19, RSV, and Influenza in Arizona: Correlation with Reported and Syndromic Cases, 2020–2025 Patrick Montine* Patrick Montine Montine Montine Montine Arizona Department of Health Services, Office of Infectious Disease Services, Phoenix, AZ, United States
Background:
Wastewater-based surveillance has become an increasingly important component of respiratory disease monitoring, offering a population-level signal that is less dependent on healthcare utilization and testing practices. This project evaluates how well wastewater viral concentrations for the effectiveness of COVID-19, RSV (respiratory syncytial virus), and Flu (Influenza A and B) track reported case and syndromic surveillance trends across Arizona during 2020-2025, and assesses the performance of legacy versus automated laboratory methods.
Methods:
We conducted an ecological study using wastewater viral concentration data and reported COVID-19, RSV, or Flu case/syndromic data. Sewersheds were aggregated at the state level and the population weighted. Rolling 7-day and weekly averages of normalized wastewater concentrations were calculated. Pearson and Spearman correlation analyses were performed to evaluate associations between wastewater viral activity and reported case trends, and to compare an older laboratory method with a newer automated method.
Results:
Across all pathogens, the automated wastewater method demonstrated consistently stronger correlations with reported cases and weekly averages than the old method. For COVID-19, correlations improved from moderate (old rolling ρ = 0.60, r = 0.66; weekly ρ = 0.71, r = 0.80) to stronger with the new method (rolling ρ = 0.70, r = 0.70; weekly ρ = 0.80, r = 0.83). Similar improvements were observed for influenza A and B, where correlations increased substantially with the automated method, and for RSV, where weak or negative correlations using the old method shifted to strong positive correlations for rolling averages using the new method (ρ = 0.87; r = 0.88).
Conclusions:
Wastewater surveillance reflects population-level respiratory disease trends, with improved methods enhancing performance and supporting its use as a scalable, resilient tool for routine monitoring and lead–lag analyses for early warning.