SARS-CoV-2 infection dynamics and genomic surveillance reveals early variant transmission in urban wastewater

Environmental surveillance (ES) of a pathogen is crucial for understanding the community load of disease. As an early warning system, ES for SARS-CoV-2 has complemented routine diagnostic surveillance by capturing near real-time virus circulation at a population level. In this longitudinal study in 28 sewershed sites in Bangalore city, we quantified SARS-CoV-2 RNA to track infection dynamics and provide evidence of change in the relative abundance of emerging variants. We describe an early warning system using the exponentially weighted moving average control chart and demonstrate how SARS-CoV-2 RNA concentrations in wastewater correlated with clinically diagnosed new COVID-19 cases, with the trends appearing 8-14 days earlier in wastewater than in clinical data. This was further corroborated by showing that the estimated number of infections is strongly correlated with SARS-CoV-2 RNA copies detected in the wastewater. Using a deconvolution matrix, we detected emerging variants of concern up to two months earlier in wastewater samples. In addition, we found a huge diversity in variants detected in wastewater compared to clinical samples. Our study highlights that quantifying viral titres, correlating it with a known number of cases in the area, and combined with genomic surveillance helps in tracking VOCs over time and space, enabling timely and making informed policy decisions.

Validating saliva as a biological sample for cost-effective, rapid and routine screening for SARS-CoV-2

PurposeCompared to nasopharyngeal/oropharyngeal swabs, non-invasive saliva samples have enormous potential for scalability and routine population screening of SARS-CoV-2. In this study, we are investigating the efficacy of saliva samples relative to nasopharyngeal/oropharyngeal swabs for use as a direct source for the RT-PCR based SARS-CoV-2 detection. MethodsPaired nasopharyngeal/oropharyngeal swabs and saliva samples were collected from suspected positive SARS-CoV-2 patients and tested using RT-PCR. Generalised linear models were used to investigate factors that explain result agreement. Further, we used simulations to evaluate the effectiveness of saliva-based screening in restricting the spread of infection in a large campus such as an educational institution. ResultsWe observed 75.4% overall result agreement. Prospective positive samples stored for three or more days showed a drastic reduction in the probability of result agreement. We observed 83% result agreement and 74.5% test sensitivity in samples processed and tested within two days of collection. Our simulations suggest that a test with 75% sensitivity, but high daily capacity can be very effective in limiting the size of infection clusters in a workspace. Guided by these results, we successfully implemented a saliva-based screening in the Bangalore Life Sciences Cluster (BLiSC) campus. ConclusionThese results suggest that saliva may be a viable sample source for SARS-CoV-2 surveillance if samples are processed immediately. We strongly recommend the implementation of saliva-based screening strategies for large workplaces and in schools, as well as for population-level screening and routine surveillance as we learn to live with the SARS-CoV-2 virus.

S Gene Target Failure (SGTF) in Commercial Multiplex RT-PCR assay as indicator to detect SARS-CoV-2 VOC B.1.1.7 lineage in Tamil Nadu, India

Emergence of Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2) Variants of Concern (VOC) possessing improved virulence, transmissibility and/or immune-escape capabilities has raised significant public health concerns. In order to identify VOCs, WHO recommends Whole-Genome Sequencing approach, which is costly and involves longer completion time. Hence, potential role of commercial multiplex RT-PCR kit to screen variants rapidly is being attempted in this study. A total of 1200 suspected COVID samples from different districts of Tamil Nadu State (India) were screened with Thermo TaqPath RT-PCR kit and Altonas Realstar RT-PCR Assay kit. Among 1200 screened, S-gene target failure (SGTF) phenomenon were identified in 112 samples while testing with TaqPath RT-PCR Kit. 100% concordant results were observed between SGTF phenomenon and whole-genome sequencing (WGS) results in detecting SARS-CoV-2 VOC B.1.1.7. TaqPath RT-PCR assay testing can be utilized by laboratories to screen rapidly the VOC B.1.1.7 variants, thus enabling early detection of B.1.1.7 variant infection and transmission in population. This in turn will pave way to implement suitable preventive measures by appropriate authorities to control the transmission of the viral variant.

Tapestry: A Single-Round Smart Pooling Technique for COVID-19 Testing

The COVID-19 pandemic has strained testing capabilities worldwide. There is an urgent need to find economical and scalable ways to test more people. We present Tapestry, a novel quantitative nonadaptive pooling scheme to test many samples using only a few tests. The underlying molecular diagnostic test is any real-time RT-PCR diagnostic panel approved for the detection of the SARS-CoV-2 virus. In cases where most samples are negative for the virus, Tapestry accurately identifies the status of each individual sample with a single round of testing in fewer tests than simple two-round pooling. We also present a companion Android application BYOM Smart Testing which guides users through the pipetting steps required to perform the combinatorial pooling. The results of the pooled tests can be fed into the application to recover the status and estimated viral load for each individual sample. NOTE: This protocol has been validated with in vitro experiments that used synthetic RNA and DNA fragments and additionally, its expected behavior has been confirmed using computer simulations. Validation with clinical samples is ongoing. We are looking for clinical collaborators with access to patient samples. Please contact the corresponding author if you wish to validate this protocol on clinical samples.

Ethyl (2E,4E)-5-(3-bromo-phenyl-sulfon-yl)penta-2,4-dienoate.

In the title compound, C13H13BrO4S, both C=C double bonds adopt an E conformation. The S atom has a distorted tetra-hedral geometry with bond angles ranging from 102.17 (13) to 119.77 (14)°. The ethyl acrylate substituent adopts an extented conformation with all torsion angles close to 180°. In the crystal, mol-ecules are linked into centrosymmetric R 2 (2)(14) dimers via pairs of C-H⋯O hydrogen bonds.

(2E,4E)-Ethyl 5-(phenyl-sulfon-yl)penta-2,4-dienoate.

In the title compound, C(13)H(14)O(4)S, both C=C double bonds adopt an E conformation. In the crystal, mol-ecules are linked into centrosymmetric R(2) (2)(14) dimers via pairs of C-H⋯O hydrogen bonds.