Decay of SARS-CoV-2 and surrogate murine hepatitis virus RNA in untreated wastewater to inform application in wastewater-based epidemiology

Abstract

Wastewater-based epidemiology (WBE) demonstrates potential for COVID-19 community transmission monitoring; however, data on the stability of SARS-CoV-2 RNA in wastewater are needed to interpret WBE results. The decay rates of RNA from SARS-CoV-2 and a potential surrogate, murine hepatitis virus (MHV), were investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in untreated wastewater, autoclaved wastewater, and dechlorinated tap water stored at 4, 15, 25, and 37 °C. Temperature, followed by matrix type, most greatly influenced SARS-CoV-2 RNA first-order decay rates ( k ). The average T 90 (time required for 1-log 10 reduction) of SARS-CoV-2 RNA ranged from 8.04 to 27.8 days in untreated wastewater, 5.71 to 43.2 days in autoclaved wastewater, and 9.40 to 58.6 days in tap water. The average T 90 for RNA of MHV at 4 to 37 °C ranged from 7.44 to 56.6 days in untreated wastewater, 5.58–43.1 days in autoclaved wastewater, and 10.9 to 43.9 days in tap water. There was no statistically significant difference between RNA decay of SARS-CoV-2 and MHV; thus, MHV is suggested as a suitable persistence surrogate. Decay rate constants for all temperatures were comparable across all matrices for both viral RNAs, except in untreated wastewater for SARS-CoV-2, which showed less sensitivity to elevated temperatures. Therefore, SARS-CoV-2 RNA is likely to persist long enough in untreated wastewater to permit reliable detection for WBE application.

The detection and stability of the SARS-CoV-2 RNA biomarkers in wastewater influent in Helsinki, Finland

“…It is important to determine the effect of storage conditions on the reliability of the SARS-CoV-2 RNA results as there is usually always a time lag between the sampling and the start of the laboratory examination due to the transportation and other logistical arrangements ( Medema et al, 2020a ). So far, the persistence of SARS-CoV-2 RNA in stored wastewater samples has only been studied at higher temperatures, 4 °C, 15 °C, 25 °C, and 37 °C ( Ahmed et al, 2020b ) and at 20 °C, 50 °C, and 70 °C ( Bivins et al, 2020 ). Furthermore, some stability information is obtained from other coronaviruses, like human coronavirus 229E ( Gundy et al, 2008 ) and SARS-CoV-1 ( Wang et al, 2005 ), or from surrogate organisms, such as murine hepatitis virus (MHV) ( Casanova et al, 2009 ; Ye et al, 2016 ).…”

Technical framework for wastewater-based epidemiology of SARS-CoV-2 based on relative quantification via qPCR

“…It worth noting that the decay kinetics of biomarkers in wastewater is an important factor to be considered whether it is relative or absolute quantification. The biomarkers (reference microbe or the virus) will decay exponentially with time in sewage of given composition [27,39].…”

“…Pasteurization can delay the decay kinetics of virus in sewage via eliminating bacterial extracellular enzyme activity and protozoan or metazoan predation [42]. Recently, Ahmed et al reported the decay kinetics of SARS-CoV-2 in pasteurized and unpasteurized sewage [39]. We extracted the decay kinetics data of SARS-CoV-2 RNA in unpasteurized sewage from Table 3 in their paper.…”

“…The decay kinetics of biomarkers (target or reference genes) in sewage can be studied via microcosm experiments in the laboratory [39]. Freshly collected sewage samples will be spiked with certain number of biomarkers (bacteria, bacteriophages, or inactivated SARS-CoV-2 virions) and incubated at certain temperature.…”

“…The calculated values of T50 and T90 are compared with experimental ones (D). The experimental data of the decay kinetics of SARS-CoV-2 RNA are available in reference[39].…”