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Decay of infectious SARS-CoV-2 and the accompanying RNA signal in ambient waters and wastewater
Citation:
Korajkic, A., B. McMinn, A. Pemberton, AND J. Kelleher. Decay of infectious SARS-CoV-2 and the accompanying RNA signal in ambient waters and wastewater. 2022 ASM Microbe Meeting, Washington, DC, June 09 - 13, 2022.
Impact/Purpose:
The research projects described persistence of infectious SARS-CoV-2 and the RNA signal in different sample types (ambient water and wastewater) and under the influence of three temperature regimes (4, 25 and 37C).
Description:
Ongoing COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused over 5.5 million deaths worldwide as of January 18th, 2022. While SARS-CoV-2 is primarily transmitted through inhalation of aerosols and droplets, it is also excreted in feces and has been frequently detected in wastewater which led to surveillance programs to estimate community infection levels. However, to date, there is limited information regarding decay characteristics of SARS-CoV-2 in the environment, including wastewater and ambient waters. Considering that untreated and partially treated wastewater can contaminate surface waters via many pathways, it is important to understand the persistence of SARS-CoV-2 under these settings. Infectious SARS-CoV-2 (Washington State strain, USA/WA1/2020) was seeded in autoclaved primary wastewater effluent, final dechlorinated wastewater effluent, lake water and artificial marine water at a final concentration of 6.26 ± 0.07 log10 plaque forming units (PFU)/mL and incubated at 4°, 25° and 37°C for two weeks. Ten subsamples were collected over the course of the study and analyzed for infectious virions via a plaque assay using the Vero E6 cell line and viral RNA was quantified with the CDC N1 and N2 RT-qPCR assays. Initial loss (within 10 minutes of seeding) ranged from 77-96% for infectious virus, and between 14 and 95% for viral RNA, depending on the sample type and temperature combination. The decay of infectious virus was significantly faster (p < 0.05) compared to RNA, irrespective of the incubation conditions and the sample type. Temperature was the most significant driver of decay (p < 0.05), and after 24h, no infectious SARS-CoV-2 was detected at 37°C. Sample type had less of an impact, with decay generally faster in wastewater compared to ambient waters. SARS-CoV-2 RNA remained detectable for the duration of the study under all study conditions and was less influenced by temperature. Our results indicate that SARS-CoV-2 RNA can persist for at least two weeks under all incubation conditions, which can permit reliable detection for wastewater-based surveillance efforts. The decay of infectious SARS-CoV-2 was significantly faster compared to the RNA signal, and temperature dependent with faster decay observed at 37°C compared to 4°C. Furthermore, while decay of infectious SARS-CoV-2 was generally faster in wastewater compared to ambient waters, this difference was temperature-dependent and not significant (p > 0.05).