Assessing PMMoV as a faecal marker for wastewater-based surveillance - Insights from Swedish wastewaters and foods

Pepper Mild Mottle Virus (PMMoV) is widely used in wastewater-based surveillance (WBS) as a faecal indicator, population size marker and analytical process control. It is highly abundant in domestic wastewater and originates from consumption of products containing Capsicum species infected with PMMoV. However, despite its widespread use in WBS, data on the variability of PMMoV levels in wastewater are limited, and the main dietary sources are not fully investigated. In this study, we assessed the reliability of PMMoV as a faecal marker by analysing wastewater samples collected across multiple locations and timeframes in Sweden. We also analysed different foods to identify possible dietary sources. Our results showed consistently high PMMoV levels in wastewater, averaging 10.37 log10 genome copies per resident per day, with overall little variation between days, weeks, and years. Of 60 foods tested, 45 contained detectable levels of PMMoV, with particularly high concentrations, ranging from 5.70 to 12.21 log10 genome copies per serving, found in commonly consumed spices, including paprika powder, and various processed foods, including ready meals, sandwich spreads and snack products. These results highlight the dietary basis for the high and stable presence of PMMoV in domestic wastewater and emphasise its robustness as a faecal marker in the Swedish context.