Persistence of endogenous RNA biomarkers of SARS-CoV-2 and PMMoV in raw wastewater: Impact of temperature and implications for wastewater-based epidemiology

Abstract

Understanding the persistence of SARS-CoV-2 biomarkers in wastewater should guide wastewater-based epidemiology users in selecting best RNA biomarkers for reliable detection of the virus during current and future waves of the pandemic. In the present study, the persistence of endogenous SARS-CoV-2 were assessed during one month for six different RNA biomarkers and for the pepper mild mottle virus (PMMoV) at three different temperatures (4, 12 and 20 °C) in one wastewater sample. All SARS-CoV-2 RNA biomarkers were consistently detected during 6 days at 4° and differences in signal persistence among RNA biomarkers were mostly observed at 20 °C with N biomarkers being globally more persistent than RdRP, E and ORF1ab ones. SARS-CoV-2 signal persistence further decreased in a temperature dependent manner. At 12 and 20 °C, RNA biomarker losses of 1-log₁₀ occurred on average after 6 and 4 days, and led to a complete signal loss after 13 and 6 days, respectively. Besides the effect of temperature, SARS-CoV-2 RNA signals were more persistent in the particulate phase compared to the aqueous one. Finally, PMMoV RNA signal was highly persistent in both phases and significantly differed from that of SARS-CoV-2 biomarkers. We further provide a detailed overview of the latest literature on SARS-CoV-2 and PMMoV decay rates in sewage matrices.

Keywords: Biomarkers partitioning; Decay rate; PMMoV; SARS-CoV-2; Wastewater-based epidemiology.

Graphical abstract

Fig. 1

Decay of SARS-CoV-2 RNA biomarkers (N1, N2, N3, E, RdRP and ORF1ab) and PMMoV in the aqueous phase according to temperature (4, 12 and 20 °C, represented by blue, orange, and red lines, respectively). Grey dashed lines symbolise the maximum decay that can be measured (see material and methods for details). Cq values and positivity rates are summarized in Table S2.

Fig. 2

Decay of SARS-CoV-2 RNA biomarkers (N1, E) and PMMoV in the particulate phase according to temperature (4, 12 and 20 °C, represented by blue, orange, and red lines, respectively). Grey dashed lines symbolise the maximum decay that can be measured (see material and methods for details). Cq values and positivity rates are summarized in Table S2.

Fig. 3

Comparison of the decay rates of the SARS-CoV-2 and PMMoV biomarkers in aqueous phase (average ± their 95 % confidence intervals) for the three incubation temperatures.