Spatio-Temporal Variability of the Pepper Mild Mottle Virus Biomarker in Wastewater

TL;DR

This study examines the spatial and temporal variability of Pepper mild mottle virus in wastewater across the US to improve normalization techniques in wastewater-based epidemiology for disease monitoring.

Contribution

It provides the first detailed analysis of PMMoV variability across different locations and times, highlighting factors influencing its levels in wastewater.

Findings

Most variation attributed to geographic location.

Site-specific factors significantly influence PMMoV levels.

Understanding variability can improve normalization in WBE.

Abstract

Since the start of the coronavirus-19 pandemic, the use of wastewater-based epidemiology (WBE) for disease surveillance has increased throughout the world. Because wastewater measurements are affected by external factors, processing WBE data typically includes a normalization step in order to adjust wastewater measurements (e.g. viral RNA concentrations) to account for variation due to dynamic population changes, sewer travel effects, or laboratory methods. Pepper mild mottle virus (PMMoV), a plant RNA virus abundant in human feces and wastewater, has been used as a fecal contamination indicator and has been used to normalize wastewater measurements extensively. However, there has been little work to characterize the spatio-temporal variability of PMMoV in wastewater, which may influence the effectiveness of PMMoV for adjusting or normalizing WBE measurements. Here, we investigate its variability across space and time using data collected over a two-year period from sewage treatment plants across the United States. We find that most variation in PMMoV measurements can be attributed to longitude and latitude followed by site-specific variables. Further research into cross-geographical and -temporal comparability of PMMoV-normalized pathogen concentrations would strengthen the utility of PMMoV in WBE.