Defining biological and biophysical properties of SARS-CoV-2 genetic material in wastewater

SARS-CoV-2 genetic material has been detected in raw wastewater around the world throughout the COVID-19 pandemic and has served as a useful tool for monitoring community levels of SARS-CoV-2 infections. SARS-CoV-2 genetic material is highly detectable in a patient's feces and the household wastewater for several days before and after a positive COVID-19 qPCR test from throat or sputum samples. Here, we characterize genetic material collected from raw wastewater samples and determine recovery efficiency during a concentration process. We find that pasteurization of raw wastewater samples did not reduce SARS-CoV-2 signal if RNA is extracted immediately after pasteurization. On the contrary, we find that signal decreased by approximately half when RNA was extracted 24-36 h post-pasteurization and similar to 90% when freeze-thawed prior to concentration. As a matrix control, we use an engineered enveloped RNA virus. Surprisingly, after concentration, the recovery of SARS-CoV-2 signal is consistently higher than the recovery of the control virus leading us to question the nature of the SARS-CoV-2 genetic material detected in wastewater. We see no significant difference in signal after different 24-hour temperature changes; however, treatment with detergent decreases signal similar to 100-fold. Furthermore, the density of the samples is comparable to enveloped retrovirus particles, yet, interestingly, when raw wastewater samples were used to inoculate cells, no cytopathic effects were seen indicating that wastewater samples do not contain infectious SARS-CoV-2. Together, this suggests that wastewater contains fully intact enveloped particles. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

The genetic material of SARS-CoV-2 has been detected in raw wastewater around the world during the COVID-19 pandemic, showing high detectability in feces and household wastewater both before and after a positive qPCR test. However, the study found that pasteurization of raw wastewater did not reduce the SARS-CoV-2 signal if RNA was extracted immediately after, with a decrease in signal observed when extraction was delayed. Surprisingly, the recovery of SARS-CoV-2 signal after concentration was consistently higher than that of a control virus, indicating potential differences in the nature of the genetic material detected in wastewater.