Changes in the Association Between Wastewater SARS-CoV-2 and Clinical Indicators Following the U.S. Public Health Emergency

The end of the U.S. Public Health Emergency (PHE) for COVID-19 altered national surveillance, shifting focus from case counts to hospital admissions and emergency department (ED) visits. However, the reliability of these clinical indicators at the local level in the post-PHE era remains unclear. To address this gap, this study examined the relationships among reported cases, ED visits, and hospital admissions across pre- and post-PHE periods, using wastewater-based epidemiology (WBE) as a stable, independent benchmark of community transmission. Between October 2022 and August 2024, 820 wastewater samples were collected from six pumping stations and quantified for SARS-CoV-2 using RT-qPCR. County-level clinical data were then compared to wastewater using time-lagged cross-correlation, ratio analyses, and change point detection. Results showed that coherence among clinical indicators weakened markedly after the PHE, with a structural break detected just 12 days later. Correlations between wastewater and hospital admissions declined sharply (r=0.90 to r=0.38), while wastewater and reported cases remained strongly correlated (r=0.79) but showed a more than 60% reduction in ratio values, indicating diminished quantitative reliability. In contrast, within this study area, ED visits emerged as the most stable metric, maintaining both a strong temporal correlation (r=0.80) and a consistent quantitative ratio with wastewater (p=0.306). Overall, these findings identify ED visits as the most reliable clinical indicator in this jurisdiction for monitoring community transmission in the post-PHE era. The declining utility of hospital admissions and case counts underscores the value of WBE as a resilient, unbiased surveillance tool. Future frameworks should integrate wastewater data with locally validated clinical indicators to sustain situational awareness. • Clinical surveillance metrics decoupled after the U.S. health emergency ended. • ED visits proved to be the most stable clinical indicator in the post-PHE era. • Hospital admissions lost their correlation with wastewater SARS-CoV-2 signals. • Case counts remained correlated but lost significant quantitative reliability. • Wastewater serves as an unbiased benchmark for validating clinical data streams.