Molecular accuracy vs antigenic speed: SARS-CoV-2 testing strategies.

The pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has hit every corner of the world faster than any infectious disease ever known. In this context, rapid and accurate testing of positive cases are essential to follow the test-trace-isolate strategy (TETRIS), which has proven to be a key approach to constrain viral spread. Here, we discuss how to interpret and combine molecular or/and antigen-based detection methods for SARS-CoV-2 as well as when they should be used. Their application can be cleverly designed as an algorithm to prevent viral dissemination according to distinct epidemiological contexts within surveillance programs.

An evolutionary insight into Severe Acute Respiratory Syndrome Coronavirus 2 Omicron variant of concern.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel virus that belongs to the family Coronaviridae. This virus produces a respiratory illness known as coronavirus disease 2019 (COVID-19) and is to blame for the pandemic of COVID-19. Due to its massive circulation around the world and the capacity of mutation of this virus, genomic studies are much needed in to order to reveal new variants of concern (VOCs). On November 26th, 2021, the WHO announced that a new SARS-CoV-2 VOC, named Omicron, had emerged. In order to get insight into the emergence, spread and evolution of Omicron SARS-CoV-2 variants, a comprehensive phylogenetic study was performed. The results of these studies revealed significant differences in codon usage among the S genes of SARS-CoV-2 VOCs Alfa, Beta, Gamma, Delta and Omicron, which can be linked to SARS-CoV-2 genotypes. Omicron variant did not evolve out of one of the early VOCs, but instead it belongs to a complete different genetic lineage from previous ones. Strains classified as Omicron variants evolved from ancestors that existed around May 15th, 2020, suggesting that this VOC may have been circulating undetected for a period of time until its emergence was observed in South Africa. A rate of evolution of 5.61 × 10-4 substitutions/site/year was found for Omicron strains enrolled in these analyses. The results of these studies demonstrate that S genes have suitable genetic information for clear assignment of emerging VOCs to its specific genotypes.

Phylogenetic analysis of SARS-CoV-2 viruses circulating in the South American region: Genetic relations and vaccine strain match.

The pandemic of coronavirus disease 2019 (COVID-19) is caused by a novel member of the family Coronaviridae, now known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Recent studies revealed the emergence of virus variants with substitutions in the spike and/or nucleocapsid and RNA-dependent RNA polymerase proteins that are partly responsible for enhanced transmission and reduced or escaped anti-SARS-CoV-2 antibodies that may reduce the efficacy of antibodies and vaccines against the first identified SARS-CoV-2 strains. In order to gain insight into the emergence and evolution of SARS-CoV-2 variants circulating in the South American region, a comprehensive phylogenetic study of SARS-CoV-2 variants circulating in this region was performed. The results of these studies revealed sharp increase in virus effective population size from March to April of 2020. At least 62 different genotypes were found to circulate in this region. Variants of concern (VOCs) Alpha, Beta, Gamma and Delta co-circulate in the region, together with variants of interest (VOIs) Lambda, Mu and Zeta. Most of SARS-CoV-2 variants circulating in the South American region belongs to B.1 genotypes and have substitutions in the spike and/or nucleocapsid and polymerase proteins that confer high transmissibility and/or immune resistance. 148 amino acid positions of the spike protein and 70 positions of the nucleocapsid were found to have substitutions in different variants isolated in the region by comparison with reference strain Wuhan-Hu-1. Significant differences in codon usage among spike genes of SARS-CoV-2 strains circulating in South America was found, which can be linked to SARS-CoV-2 genotypes.