Population Normalization in SARS-CoV-2 Wastewater-Based Epidemiology: Implications from Statewide Wastewater Monitoring in Missouri

Abstract

The primary objective of this study was to identify a universal wastewater biomarker for population normalization for SARS-CoV-2 wastewater-based epidemiology (WBE). A total of 2,624 wastewater samples (41 weeks) were collected weekly during May 2021- April 2022 from 64 wastewater facilities across Missouri, U.S. Three wastewater biomarkers, caffeine and its metabolite, paraxanthine, and pepper mild mottle virus (PMMoV), were compared for the population normalization effectiveness for wastewater SARS-CoV-2 surveillance. Paraxanthine had the lowest temporal variation and strongest relationship between population compared to caffeine and PMMoV. This result was confirmed by data from ten different Wisconsin WWTPs with gradients in population sizes, indicating paraxanthine is a promising biomarker of the real-time population across a large geographical region. The estimated real-time population was directly compared against the population patterns with human movement mobility data. Of the three biomarkers, population normalization by paraxanthine significantly strengthened the relationship between wastewater SARS-CoV-2 viral load and COVID-19 incidence rate the most (40 out of 61 sewersheds). Caffeine could be a promising population biomarker for regions where no significant exogenous caffeine sources (e.g., discharges from food industries) exist. In contrast, PMMoV showed the highest variability over time, and therefore reduced the strength of the relationship between sewage SARS-CoV-2 viral load and the COVID-19 incidence rate, as compared to wastewater data without population normalization and the population normalized by either recent Census population or the population estimated based on the number of residential connections and average household size for that municipality from the Census. Overall, the findings of this long-term surveillance study concluded that the paraxanthine has the best performance as a biomarker for population normalization for SARS-CoV-2 wastewater-based epidemiology.

Graphene Multiplexed Sensor for Point-of-Need Viral Wastewater-Based Epidemiology

“…These include caffeine, paraxanthine (caffeine’s metabolite), creatine, 5-hydroxyindoleacetic acid (5-HIAA, serotonin metabolite), and pepper mild mottle virus (PMMoV) given their ubiquitousness in human diets and survivability in wastewater (Hsu et al 2022). Paraxanthine and PMMoV concentration, in particular, are excellent means for population normalization (C. Li et al 2022b). Unfortunately, to the best of our knowledge, no aptamer has yet been developed for PMMoV or paraxanthine.…”

“…Similarly challenging is the need to multiplex assays or testing strategies to monitor multiple targets to reduce cost, time, and effort while addressing seasonal and population variations via normalization. For point-of-need WBE sensing, population normalization is crucial due to increased variability in dilution factors, such as per capita water use, stormwater inputs, etc., and viral shedding rates (Sweetapple et al 2023; Rainey et al 2023; C. Li et al 2022a). This variability exacerbates the already challenging task of calculating the number of people infected based solely on the virus concentration in the wastewater sample.…”

Wastewater-Based Epidemiology of SARS-CoV-2 and Other Respiratory Viruses: Bibliometric Tracking of the Last Decade and Emerging Research Directions

“…Normalizing viral concentrations in wastewater based on the amount of human feces is crucial for interpreting and comparing viral levels over time. Pepper mild mottle virus (PMMoV), a commonly found RNA virus in human fecal material, was utilized for WBE data normalization due to its higher concentrations in wastewater [58]. It can be quantified simultaneously with targeted respiratory viruses using multiplexed assays.…”

Quantitatively assessing early detection strategies for mitigating COVID-19 and future pandemics

“…These three sites have attracted interest because they have been frequent testing sites in COVID-19: hospitals since the pandemic's beginning 30 , and wastewater (including wastewater at treatment plants 20 , within the sewershed 31 , and locally near individual buildings 32 ) and air travel more recently 33,34 because hospital cases can lag community cases 35 . COVID-19 also spurred methodological innovation and characterization of sampling from these sites 36 , particularly wastewater [37][38][39] . Detecting novel pandemics at these sites has occasionally been piloted 21,40 but has not been implemented at scale, in part because it is unclear if these proposed systems sufficiently expedite detection of outbreaks.…”