A-233 Wastewater-based surveillance for SARS-CoV-2 Subvariants using the Nanopore Sequencing in South Korea

Abstract

Abstract Background Genomic tools to identify and characterize SARS-CoV-2 and its various subvariants were adapted from clinical settings. Wastewater-based surveillance (WBS) has since been recognized as tool of transformative potential, providing real-time objective, comprehensive data on the prevalence and distribution of the target pathogen across the space and time. We conducted wastewater-based epidemiology (WBE) at sewage treatment plants to find a more efficient mutation monitoring method, and respond to pre-existing infectious diseases. Methods In our study, domestic sewage collected every weeks from 6 sewage treatment plants in urban region from June 2023 to November 2023 was used to concentrate and isolate viruses using wastewater ultra nucleic acid isolation kits with virus enrichment kits. Positive samples confirmed were subjected to SARS-CoV-2 whole genome sequencing (WGS) using GridION (Oxford Nanopore Technologies). The experimental data was aligned through Epi2me, analyzed using Nextclade, that was compared with KCDC official reports and our monitoring results (total 780 cases) ongoing at SCL. Results Various mutations were identified at each collection time, occurring new subvariants over time. The mutations (orf1a:A690V, S:F456L) sequentially confirmed from the sample collected on Aug. 23rd are specific mutations of XBB.1.9.2 and EG.5. In addition, the mutations orf1b: D54N, S:L455F, which were sequentially confirmed from the sample collected on Sep. 6th, are HK.3, a descendent lineage of EG.5, and FLip variants, which show growth advantage, were confirmed. Furthermore, the detection rate of FLip variants detected from Sep.6th gradually increased from 17% to 67% (Fig.1). Taken together, we confirmed the similarity between monthly detected mutations and changes in dominant species over time by comparing with ‘monthly COVID-19 mutation trends’ and ‘HK.3 dominance announcement by KCDC’(Fig.2). Conclusions WBS would be a useful tool for proactively responding to infectious diseases including COVID-19 by exploring new mutations and predicting changes in dominant species.