Environmental genomic surveillance of SARS-CoV-2 in wastewater in Rio de Janeiro, Brazil

Environmental Dissemination of SARS-CoV-2: An Analysis Employing Crassphage and Next-Generation Sequencing Protocols

This study aimed to investigate the dissemination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in water samples obtained during the coronavirus disease 2019 pandemic period, employing cross-assembly phage (crAssphage) as a fecal contamination biomarker and next-generation sequencing protocols to characterize SARS-CoV-2 variants. Raw wastewater and surface water (stream and sea) samples were collected for over a month in Rio de Janeiro, Brazil. Ultracentrifugation and negatively charged membrane filtration were employed for viral concentration of the wastewater and surface water samples, respectively. Viruses were detected and quantified by (RT-)qPCR applying TaqMan® system protocols. SARS-CoV-2 RNA signals were detected in 92.5% (37/40) of the wastewater samples and in 31.25% (10/32) of the stream water samples, but not in seawater samples. CrAssphage was detected in 100% of the wastewater samples, 93.75% (30/32) of the stream samples, and in 2/4 of the seawater samples. CrAssphage detection and high concentrations in stream surface waters (median 8.95 log10 gc/L) revealed diffuse contamination by domestic wastewater in a region with high sanitary coverage. The correlations detected between SARS-CoV-2 data and the moving averages of clinical cases per capita over the sampling period were moderate to strong when applying a 13-day offset, regardless of normalization by crAssphage data or not. Sequencing of the receptor-binding domain of the spike protein confirmed the detection of SARS-CoV-2, but did not characterize the circulating variant. On the other hand, the whole genome sequencing protocol identified circulation of the Gamma variant, corroborating the sampling period clinical data.

Co-occurrence of SARS-CoV-2 variants in rivers and sewage in India and Brazil

The genomic monitoring of SARS-CoV-2 variants of concern (VOCs) in riverine and sewage water has been widely used as an epidemiological tool worldwide. But its utility for epidemiological assessments still needs to be evaluated in some areas. Our study encompassed thirteen Brazilian rivers spanning a vast urban expanse across the states of Rio de Janeiro, São Paulo, and Paraná. The sampled rivers in Rio de Janeiro are heavily contaminated with sewage. Meanwhile, the Indian samples were all wastewater before joining the water bodies from urban regions (Andhra Pradesh and Telangana). The viral copies were quantified using quantitative polymerase chain reaction (qPCR) in all examined samples (N = 91). The abundance of viral particles varied from 567 to 85,700,000 copies/ml. Subsequently, Illumina CovidSeq was applied to identify the major variants. In Brazil, while a single SARS-CoV-2 VOC was identified for just a few samples (6/50, 12 %), most samples harbored multiple VOCs (44/50, 88 %). In India only one probed sample had a single variant identified. Gamma (2021) and Omicron (2021 and 2022) were the most abundant variants. Delta and Omicron genetic material were detected in Rio de Janeiro city rivers before Brazil's first cases of these variants. Several negative samples in the Real-Time RT-PCR (qPCR) turned out to have SARS-CoV-2 sequences suggesting CovidSeq was more sensitive than RT-PCR for virus detection in environmental samples. Sewage surveillance holds promise for early detection of emerging variants driving pandemic waves, exemplified by the Delta and Omicron variants, potentially offering a preemptive advantage over clinical sample reports.

Prevalence of SARS-CoV-2 variants in Prague wastewater determined by nanopore-based sequencing

The early detection of upcoming disease outbreaks is essential to avoid both health and economic damage. The last four years of COVID-19 pandemic have proven wastewater-based epidemiology is a reliable system for monitoring the spread of SARS-CoV-2, a causative agent of COVID-19, in an urban population. As this monitoring enables the identification of the prevalence of spreading variants of SARS-CoV-2, it could provide a critical tool in the fight against this viral disease. In this study, we evaluated the presence of variants and subvariants of SARS-CoV-2 in Prague wastewater using nanopore-based sequencing. During August 2021, the data clearly showed that the number of identified SARS-CoV-2 RNA copies increased in the wastewater earlier than in clinical samples indicating the upcoming wave of the Delta variant. New SARS-CoV-2 variants consistently prevailed in wastewater samples around a month after they already prevailed in clinical samples. We also analyzed wastewater samples from smaller sub-sewersheds of Prague and detected significant differences in SARS-CoV-2 lineage progression dynamics among individual localities studied, e.g., suggesting faster prevalence of new variants among the sites with highest population density and mobility.