Tracking COVID-19 trends in communities with low population by wastewater-based surveillance

Wastewater-based surveillance (WBS) of SARS-CoV-2 is increasingly recognized as a valuable complement to clinical reporting for estimating COVID-19 infection rates. This acceptance stems from the strong correlation found between wastewater and clinical case data during the early stages of the pandemic. However, the cessation of COVID-19 restrictions, changes in clinical testing requirements by late 2021, and the widespread use of take-home antigen tests have diminished the reliability and volume of clinically reported case counts. This study explores the dynamics between clinical cases and wastewater-based results in a period of transition, focusing on student residential areas within a university campus. We analyzed wastewater from 13 sub-sewersheds, serving populations of 300 to 4000 individuals, three times weekly from December 2021 to June 2022. The analysis revealed two COVID-19 spikes in wastewater data during this time, whereas clinical reports indicated at most a single surge in infections across most communities. Further, in the first infection surge, clinical data plateaued sooner than wastewater trends and, in the second surge, either lagged or were completely absent. Correlations between wastewater SARS-CoV-2 concentrations and the 3-day rolling average of clinical cases were weak in smaller communities (≤1000 people) but improved with larger community sizes (>1000 people). Normalization with PMMoV did not enhance these correlations. Given the challenges in executing widespread and accurate mass clinical testing, our findings advocate for the efficacy of WBS data in reliably forecasting infection surges, even in less populous settings, thereby facilitating swift, informed public health interventions.