Challenges for COVID-19 surveillance through wastewater-based epidemiology in post-pandemic era: A retrospective study in 222 USA counties

The post-pandemic world still faces ongoing COVID-19 infections, where wastewater-based epidemiology (WBE) is recognized as an efficient tool for the population-wide surveillance of COVID-19 infections. Utilizing weekly county-level wastewater-surveillance data during pandemic across 222 counties from 49 states in United States of America (USA) from June 2021-November 2022 and covering 104 M populations, we retrospectively evaluated the correlation between SARS-CoV-2 RNA concentrations in wastewater ( C RNA ) and reported cases as well as the impacts of demographics, socioeconomical, test accessibility, epidemiological, environmental factors and international air travelling on reported cases under the corresponding C RNA . The lift of travel restrictions in June 2022, a milestone for the post-pandemic era, shifted the correlation between C RNA and COVID-19 incidence in following 7-day and 14-day from 0.70 (IQR: 0.30-0.88) and 0.74 (IQR: 0.31-0.90) to 0.01 (IQR: -0.31-0.36) and -0.01 (IQR: -0.38-0.45), respectively. In post-pandemic period, under the same C RNA , the reported case numbers were impacted by international passengers, test accessibility, Omicron prevalence, ratio of population aged between 18-65, minority vulnerability, and healthcare system. These factors bring new challenges in post-pandemic era, which needs additional attention while using WBE surveillance for COVID-19 infections. This study facilitates public health authorities to dynamically adjust their WBE to the local context to achieve optimal community surveillance.