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

Tuning the Viscosity Profiles of High- T g Poly(1,2,3-triazolium) Covalent Adaptable Networks by the Chemical Structure of the N-Substituents

International audienceA designed library of covalent adaptable networks (CANs) having 1,2,3-triazolium dynamic cross-links are obtained through the combination of solvent- and catalyst-free thermally induced azide-alkyne cycloaddition and N-alkylation reactions. The use of rigid heterocyclic or aromatic segments affords CANs with greatly extended range of thermomechanical profiles, with Tgs up to 146 °C, dramatic changes in relaxation times (from 1.5 h to less than 2 min at 150 °C) depending on the chemical structure of the N-substituents of 1,2,3-triazolium cross-links, and tunable rubbery plateaus, with nearly constant elastic moduli up to ca. 160 °C. A detailed correlation between the rheological properties and the chemical compositions of these CANs shows that the relaxation dynamics of the networks are mainly determined by the chemical structure of the N-substituents of the 1,2,3-triazolium cross-links, and are independent both from the composition of the surrounding polymer networks and the corresponding Tg, at temperatures ranging from Tg + 20 °C to ca. 180 °C

Synthesis of new poly(ether ketone)s derived from biobased diols

International audienceThumbnail image of graphical abstract A new class of poly(ether ketone)s (PEKs) is prepared by polycondensation of various diols produced from biomass and various difluoro aromatics. After optimization of the reaction conditions, polycondensation of isosorbide and 4,4′-difluorodiphenylketone (2a) gives PEK1 with a high yield, moderate viscosity (0.31 dL g−1), and a glass-transition temperature (Tg) of 170 °C. The optimum conditions are applied to the synthesis of a series of PEKs (PEK 2-9) from difluoro agents and sugar diols. The polycondensation of isomannide (1b) with 1,4-di(p-fluorobenzoyl)benzene (2b) gives the best results with an inherent viscosity of 0.52 dL g−1 and the mass spectrum shows an abundance of cyclic structures. Similar conditions are used for the preparation of high-molar-mass copoly(ether ketone)s from a stoechiometric mixture of isosorbide/bisphenol-A

Copolyethersulfones of 1,4:3,6-dianhydrohexitols and bisphenol A

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UV-Patterning of Ion Conducting Negative Tone Photoresists Using Azide-Functionalized Poly(Ionic Liquid)s

International audienceThe patterning of solid electrolytes that builds upon traditional fabrication of semiconductors is described. An azide-, functionalized poly(1,2,3-triazolium ionic liquid) is used as an ion conducting negative tone photoresist. After UV-irradiation through an optical mask, micron-scaled, patterned, solid polyelectrolyte layers with controlled sizes and shapes are obtained. Furthermore, alkylation of poly(1,2,3-triazole)s can be generalized to the synthesis of poly(ionic liquid)s with a tunable amount of pendant functionalities

Photoresponsive Polyamides Containing Pentamethylated Norbornadiene Moieties: Synthesis and Photochemical Properties under Sunlight Irradiation

International audiencePhotoresponsive polyamides containing main-chain pentamethylated norbornadiene (NBD) moieties are obtained in quantitative yields via the Yamazaki-Higashi reaction between a pentamethylated NBD dicarboxylic acid and a series of aromatic diamines. Chemical structures are confirmed by H-1 and C-13 NMR and weight average molar masses measured by SEC are in the range of 21,500-28,600 g mol(-1) with chain dispersities close to 2. Physical properties are investigated by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, and viscosimetry. All obtained polyamides are amorphous with glass transition temperatures ranging from 68 to 124 degrees C. They are soluble at room temperature in common organic solvents and exhibit good thermal stabilities with T-d10 values ranging from 175 to 276 degrees C. The photochemical isomerization of the NBD moiety into quadricyclane (QC) is studied by UV/vis spectroscopy after sunlight irradiation of polymer films. For all polyamides, a first-order kinetic rate is observed for the conversion of NBD to QC. The thermal release of the stored energy associated to the reverse transformation of QC groups into NBD ones is about 90-95 kJ mol(-1) as measured by DSC of the irradiated polymer films

Synthesis and proton conductive properties of novel sulfonated (sulfone-triazoles) copolymers

International audienceA new bisphenol containing 1,2,3-triazole ring (BPT) was synthetized using the click reaction and copolymerized with diammonium salt of 4,4'-difluorodiphenylsulfone-3,3'-disulfonic acid (DFPSS) and 4,4'-difluorodiphenylsulfone (DFPS) to prepare new copper free sulfonated sulfone-(1,2,3-triazole) copolymers (SSTP) for use as a proton exchange membrane fuel cells. Four copolymers with different ion exchange capacity (IEC) in the range of 1 to 1.6 meqH+/g were obtained by varying the molar ratio of the 3 monomers. The structure of SSTP was confirmed by NMR. They are soluble in polar aprotic solvents such as NMP, DMF and DMSO and show good thermal properties. Membranes from three of these SSTPs were prepared using the solution casting method and characterized in order to determine their water uptake (WU) and their ionic conductivity at 80°C

Trans-N-alkylation Covalent Exchanges on 1,3,4-Trisubstituted 1,2,3-Triazolium Iodides

International audience1,3,4-Trisubstituted 1,2,3-triazolium salts having either aliphatic or benzylic substituents at the N-1 and N-3 positions were synthesized in two steps involving: i) copper(I) catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC), and ii) N-alkylation of the 1,2,3-triazole intermediates. Trans-N-alkylation reactions in bulk and in the presence of excess methyl iodide were monitored by 1H NMR spectroscopy for each 1,2,3-triazolium molecular model. By assigning the different formed species and their respective evolution with time, it was possible to conclude that trans-N-alkylation exchange reactions are significantly faster for benzylic substituents than for aliphatic ones. Furthermore, the exchange reactions are noticeably faster at the N-3 position than at the N-1 position most likely due to the steric hindrance induced by the neighboring C-4 substituent. The kinetics of trans-N-alkylation reactions are thus influenced by both the chemical nature of the N-1 and N-3 substituents and the regiochemistry of the 1,2,3-triazolium group. This provides important structural design rules to improve the properties of thermosetting covalent adaptable networks involving trans-N-alkylation of 1,2,3-triazolium salts

Delay of fibrinolysis in St- elevation myocardial infarction: Results of an investigation conducted in a single center in Sousse Tunisia

Background: The aim of our study was to assess the delay of fibrinolysis in ST elevation myocardial infarction (STEMI) in our region and to identify characteristics associated with prolonged delay. Patients and Methods: We analyzed clinical characteristics of a prospective cohort of unselected patients admitted for (STEMI). The study was conducted over three years 2007-2009 and 250 patients were included in a single center without capability of percutaneous coronary intervention. Results: The mean age of our patients was 58±13, 7 years. Ninety percent of our patients consult directly the emergency department and 61, (5%) of them were admitted within first 6 hours of onset of symptoms. Median time to reperfusion was 46 min. Predictor of this long delay to initiate fibrinolysis were inter-department decision OR 6; 95% CI 3,48-10,34, diabetes OR 2,25; 95% CI 1,28-3,96 age >58,4 years OR 1,97; 95% CI 1,19-3,25 and transfer from regional hospital to our center OR 1,78; 95% 1,03-3.07. Conclusion: These results suggest that improvement in organization health care system can shorten delay to fibrinolysis in a center without percutaneous coronary intervention capability