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

• Published in: The Science of the total environment Vol. 770; p. 145274
• Main Authors: Hokajärvi, Anna-Maria, Rytkönen, Annastiina, Tiwari, Ananda, Kauppinen, Ari, Oikarinen, Sami, Lehto, Kirsi-Maarit, Kankaanpää, Aino, Gunnar, Teemu, Al-Hello, Haider, Blomqvist, Soile, Miettinen, Ilkka T., Savolainen-Kopra, Carita, Pitkänen, Tarja
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.05.2021; The Author(s). Published by Elsevier B.V
• Subjects: Biomarkers; Communicable Disease Control; COVID-19; Decay characteristics; Finland; Humans; Municipal sewage; New coronavirus; RNA, Viral; SARS-CoV-2; Storage conditions; Wastewater; Finland; New coronavirus; Municipal sewage; Storage conditions; Decay characteristics
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.145274

Wastewater-based surveillance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is used to monitor the population-level prevalence of the COVID-19 disease. In many cases, due to lockdowns or analytical delays, the analysis of wastewater samples might only be possible after prolonged storage. In this study, the effect of storage conditions on the RNA copy numbers of the SARS-CoV-2 virus in wastewater influent was studied and compared to the persistence of norovirus over time at 4 °C, −20 °C, and −75 °C using the reverse-transcription quantitative PCR (RT-qPCR) assays E-Sarbeco, N2, and norovirus GII. For the first time in Finland, the presence of SARS-CoV-2 RNA was tested in 24 h composite influent wastewater samples collected from Viikinmäki wastewater treatment plant, Helsinki, Finland. The detected and quantified SARS-CoV-2 RNA copy numbers of the wastewater sample aliquots taken during 19–20 April 2020 and stored for 29, 64, and 84 days remained surprisingly stable. In the stored samples, the SARS betacoronavirus and SARS-CoV-2 copy numbers, but not the norovirus GII copy numbers, seemed slightly higher when analyzed from the pre-centrifuged pellet—that is, the particulate matter of the influent—as compared with the supernatant (i.e., water fraction) used for ultrafiltration, although the difference was not statistically significant. Furthermore, when wastewater was spiked with SARS-CoV-2, linear decay at 4 °C was observed on the first 28 days, while no decay was visible within 58 days at −20 °C or −75 °C. In conclusion, freezing temperatures should be used for storage when immediate SARS-CoV-2 RNA analysis from the wastewater influent is not possible. Analysis of the particulate matter of the sample, in addition to the water fraction, can improve the detection frequency. [Display omitted] •Wastewater sample aliquots during prolonged storage were investigated.•SARS-CoV-2 RNA was detected for the first time in wastewater in Helsinki, Finland.•SARS-CoV-2 RNA copy numbers were stable in cold temperatures over one to three months.•SARS-CoV-2 RNA copy number declined over 28 days at 4 °C but not at −20 °C or −75 °C.•The inclusion of particulate matter should be considered in the analysis of SARS-CoV RNA.