The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Formulation of a modified release metformin. HCl matrix tablet: influence of some hydrophilic polymers on release rate and in-vitro evaluation

Metformin hydrochloride is an antidiabetic agent which improves glucose tolerance in patients with type 2 diabetes and reduces basal plasma levels of glucose. In this study, a simplex centroid experimental design with 69 runs was used to select the best combination of some hydrophilic polymers that rendered a 24 h in-vitro release profile of metformin.HCl. The Korsmeyer-Peppas model was used to model the dissolution profiles since it presented the best fit to the experimental data. Further, a cubic model predicted the best formulation of metformin.HCl containing polyvinyl pyrrolidone, ethyl cellulose, hydroxypropyl methyl cellulose, carrageenan, sodium alginate, and gum arabic at 6.26, 68.7, 6.26, 6.26, 6.26 and 6.26 % levels, respectively. The validation runs confirmed the accuracy of the cubic model with six components for predicting the best set of components which rendered a once-a-day modified release hydrophilic matrix tablet in compliance with the USP specifications.<br>O cloridrato de metformina é um agente antidiabético que melhora a tolerância à glicose em pacientes com diabetes tipo 2 e reduz os níveis plasmáticos basais de glicose. Neste estudo, um projeto experimental do tipo "centróide simplex" com 69 tomadas foi usado para selecionar a melhor combinação de alguns polímeros hidrofílicos que gerou um perfil de liberação da metformina.HCl de 24 horas. O modelo Korsmeyer-Peppas foi usado para modelar os perfis de dissolução, uma vez que apresentou os melhores ajustes aos dados experimentais. Além disso, um modelo cúbico previu a melhor formulação de metformina.HCl sendo aquela contendo polivinilpirrolidona, etilcelulose, hidroxipropilmetil celulose, carragena, alginato de sódio e goma arábica nos níveis 6.26, 68.7, 6.26, 6.26, 6.26 e 6.26 %, respectivamente. As corridas de validação confirmaram a precisão do modelo cúbico com os seis componentes para prever o melhor conjunto de componentes que originou uma libertação do tipo "uma vez ao dia" em conformidade com as especificações da USP, a partir de comprimidos matriciais