Spatiotemporal transmission of SARS-CoV-2 lineages during 2020-2021 in Pernambuco - Brazil (preprint)

In recent years, the SARS-CoV-2 viruses emerged and spread around the world, leaving a large death toll and long-lasting impact on survivors. As of January 2023, Brazil is still among the countries with the highest number of registered deaths. This continental-size and pluralistic country experienced a heterogenous implementation of non-pharmacological and pharmacological interventions which, associated with large socioeconomic differences between the country regions, has led to distinct virus spread dynamics across the country. Here we investigate the spatiotemporal dispersion of emerging SARS-CoV-2 lineages and its dynamics in distinct epidemiological scenarios in the first two years of the pandemics in the Pernambuco state (Northeast Brazil). We generated a total of 1389 new SARS-CoV-2 genomes from June 2020 to August 2021 covering all major regions of the state. This sampling captured the arrival, communitary transmission and the circulation of the B1.1, B.1.1.28 and B.1.1.33 lineages in the first eight months of the pandemics, the emergence of the former variant of interest P.2 and the emergence and fast replacement of all previous variants by the more transmissible variant of concern P.1 (Gamma) lineage. Based on the incidence and lineage spread pattern we observed that there was an East-to-West to inner state pattern of transmission which is in agreement with the transmission of more populous metropolitan areas to medium and small size country-side cities in the state. Such transmission patterns may be partially explained by the main routes of traffic across municipalities in the state. Nevertheless, inter-state traffic was also another important source of lineage introduction and spread into the state. Our results highlight that the fine grained intrastate analysis of lineages and incidence spread can provide actionable insights for planning future non-pharmacological intervention for air-borne transmissible human pathogens.

Real-life evaluation of a rapid antigen test (DPP SARS-CoV-2 Antigen) for COVID-19 diagnosis of primary healthcare patients, in the context of the Omicron-dominant wave in Brazil (preprint)

Rapid antigen tests play an important role in the monitoring and mitigation of the COVID-19 pandemic, as it provides an easy, fast and efficient diagnosis with minimum infrastructure requirements. However, as new variants of concern continue to emerge, mutations in the virus genome may impair the recognition of the mutated antigen by the tests. Therefore, it is essential to re-assess the test's sensitivity as the virus mutation profile undergoes significant changes. Here, we prospectively accessed the performance of the DPP SARS-CoV-2 Antigen test in the context of an omicron-dominant real-life setting. We evaluated 347 unselected individuals (all-comers) from a public testing center in Brazil, performing the rapid antigen test diagnosis at point-of-care with fresh samples. The combinatory result from two distinct RT-qPCR methods was employed as reference and 13 samples with discordant PCR results were excluded. The assessment of the rapid test in 67 PCR-positive and 265 negative samples revealed an overall sensitivity of 80.5%, specificity of 99.2% and positive/negative predictive values higher than 95%. However, we observed that the sensitivity was dependent on the viral load (sensitivity in Ct<31 = 93.7%; Ct>31 = 47.4%). Furthermore, we were able to confirm that the positive samples evaluated in the study were Omicron (BA.1/BA.1.1) by whole-genome sequencing (n=40) and multiplex RT-qPCR (n=17). Altogether, the data obtained from a real-life prospective cohort supports that the rapid antigen test sensitivity for the Omicron remains high and underscores the reliability of the test for COVID-19 diagnosis in a setting with high disease prevalence and limited PCR testing capability.

A Sanger-based approach for scaling up screening of SARS-CoV-2 variants of interest and concern (preprint)

The global spread of new SARS-CoV-2 variants of concern underscore an urgent need of simple deployed molecular tools that can differentiate these lineages. Several tools and protocols have been shared since the beginning of the COVID-19 pandemic, but they need to be timely adapted to cope with SARS-CoV-2 evolution. Although whole-genome sequencing (WGS) of the virus genetic material have been widely used, it still presents practical difficulties such as high cost, shortage of available reagents in the global market, need of a specialized laboratorial infrastructure and well-trained staff. These limitations result in genomic surveillance blackouts across several countries. Here we propose a rapid and accessible protocol based on Sanger sequencing of a single PCR fragment that is able to identify and discriminate all SARS-CoV-2 variants of concern (VOCs) identified so far, according to each characteristic mutational profile at the Spike-RBD region (K417N/T, E484K, N501Y, A570D). Twelve COVID-19 samples from Brazilian patients were evaluated for both WGS and Sanger sequencing: three from P.2, two from P.1 and seven from B.1.1 lineage. All results from the Sanger sequencing method perfectly matched the mutational profile of VOCs and non-VOCs described by WGS. In summary, this approach allows a much broader network of laboratories to perform molecular surveillance of SARS-CoV-2 VOCs and report results within a shorter time frame, which is of utmost importance in the context of rapid public health decisions in a fast evolving worldwide pandemic.

Multiple introductions followed by ongoing community spread of SARS-CoV-2 at one of the largest metropolitan areas in the Northeast of Brazil (preprint)

The emergence of SARS-CoV-2 in the human population has caused a huge pandemic that is still unfolding in many countries around the world. Multiple epicenters of the pandemic have emerged since the first pneumonia cases in Wuhan, first in Italy followed by the USA and Brazil. Up to now, Brazil is the second most affected country, however, genomic sequences of SARS-CoV-2 strains circulating in the country are restricted to some highly impacted states. Although the Pernambuco state, located in the Northeast Region, is the sixth most affected brazilian state and the second considering lethality rate, there is a lack of high quality genomic sequences from the strains circulating in this region. Here, we sequenced 38 strains of SARS-CoV-2 from patients presenting Covid-19 symptoms. Phylogenetic reconstructions revealed that three lineages were circulating in the state and 36 samples belong to B1.1 lineage. We detected two introductions from European countries and five clades, corroborating the community spread of the virus between different municipalities of the state. Finally, we detected that all except one strain showed the D614G spike protein amino acid change that may impact virus infectivity in human cells. Our study brought new light to the spread of SARS-CoV-2 strains in one of the most heavily impacted states of Brazil.