This is a PDF file of a peer-reviewed paper that has been accepted for publication. Although unedited, the content has been subjected to preliminary formatting. Nature is providing this early version of the typeset paper as a service to our authors and readers. The text and figures will undergo copyediting and a proof review before the paper is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers apply.
Suppressing SARS-CoV-2 will likely require the rapid identification and isolation of infected individuals, on an ongoing basis. RT-PCR (reverse transcription polymerase chain reaction) tests are accurate but costly, making regular testing of every individual expensive. The costs are a challenge for all countries and particularly for developing countries. Cost reductions can be achieved by combining samples and testing them in groups. We propose an algorithm for grouping subsamples, prior to testing, based on the geometry of a hypercube. At low prevalence, this testing procedure uniquely identifies infected individuals in a small number of tests. We discuss the optimal group size and explain why, given the highly infectious nature of the disease, parallel searches are preferred. We report proof of concept experiments in which a positive sample was detected even when diluted a hundred-fold with negative samples. Using these methods, the costs of mass testing could be reduced by a factor of ten to a hundred or more. If infected individuals are quickly and effectively quarantined, the prevalence will fall and so will the costs of regularly testing everyone. Such a strategy provides a possible pathway to the longterm elimination of SARS-CoV-2. Field trials of our approach are now under way in Rwanda and initial data from these are reported here. * nturok@perimeterinstitute.ca † wndifon@nexteinstein.org . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)
Introduction This study aimed to assess the prevalence and associated risk factors of intestinal parasite infections among children less than two years of age in Rutsiro, Rwanda. Methods A cross-sectional parasitological survey was conducted in Rutsiro in June 2016. Fresh stool samples were collected from 353 children and examined using microscopy to detect parasite. A questionnaire was administered to collect data on hygiene, sanitation, socio-demographic and economic characteristics. Results Approximately one in two children (44.8%) were found to be infected with at least one intestinal parasite. Ascaris (28.5%) was the most prevalent infection followed by Entamoeba histolytica (25.95%) and Giardia lamblia (19.6%). Infection with more than one pathogen was noted e.g. presence of Ascaris and yeasts (8.9%), and amoeba with Trichocephale (4.4%), respectively. Children from non-farming families were less likely to be at risk of intestinal parasite infections (AOR = 0.41, p = 0.028) compared to children from farming families. Children from households with access to treated drinking water were less likely to contract intestinal parasite infections (AOR = 0.44, p = 0.021) compared with those who used untreated water. Children from families with improved sources of water were twice as likely to be diagnosed with intestinal parasitoses compared to those who did not. We postulate that the majority of families (50.1%) who have access to improved water sources do not treat water before consumption. Conclusion The high prevalence of intestinal parasitoses in children warrants strict control measures for improved sanitation, while treatment of drinking water should be considered.
Background: Coronavirus disease 2019 (COVID-19) is a highly infectious disease with significant mortality, morbidity, and far-reaching economic and social disruptions. Testing is key in the fight against COVID-19 disease. The gold standard for COVID-19 testing is the reverse transcription polymerase chain reaction (RT-PCR) test. RT-PCR requires highly specialized, expensive, and advanced bulky equipment that is difficult to use in the field or in a point of care setting. There is need for a simpler, inexpensive, convenient, portable and accurate test. Our aims were to: (i) design primer-probe pairs for use in isothermal amplification of the S1, ORF3 and ORF8 regions of the SARS-CoV2 virus; (ii) optimize the recombinase polymerase amplification (RPA) assay for the isothermal amplification of the named SARS-COV2 regions; (iii) detect amplification products on a lateral flow device. and (ii) perform a pilot field validation of RPA on RNA extracted from nasopharyngeal swabs. Results: Assay validation was done at the National Reference Lab (NRL) at the Rwanda Biomedical Center (RBC) in Rwanda. Results were compared to an established, WHO-approved rRT-PCR laboratory protocol. The assay provides a faster and cheaper alternative to rRT-PCR with 100% sensitivity, 93% specificity, and positive and negative predictive agreements of 100% and 93% respectively. Conclusion: To the best of our knowledge, this is the first in-field and comparative laboratory validation of RPA for COVID-19 disease in low resource settings. Further standardization will be required for deployment of the RPA assay in field settings. Keywords: Recombinase Polymerase Amplification, COVID-19
COVID-19 disease has had a relatively less severe impact in Africa. To understand the role of SARS CoV2 mutations on COVID-19 disease in Africa, we analysed 282 complete nucleotide sequences from African isolates deposited in the NCBI Virus Database. Sequences were aligned against the prototype Wuhan sequence (GenBank accession: NC_045512.2) in BWA v. 0.7.17. SAM and BAM files were created, sorted and indexed in SAMtools v. 1.10 and marked for duplicates using Picard v. 2.23.4. Variants were called with mpileup in BCFtools v. 1.11. Phylograms were created using Mr. Bayes v 3.2.6. A total of 2,349 single nucleotide polymorphism (SNP) profiles across 294 sites were identified. Clades associated with severe disease in the United States, France, Italy, and Brazil had low frequencies in Africa (L84S=2.5%, L3606F=1.4%, L3606F/V378I/=0.35, G251V=2%). Sub Saharan Africa (SSA) accounted for only 3% of P323L and 4% of Q57H mutations in Africa. Comparatively low infections in SSA were attributed to the low frequency of the D614G clade in earlier samples (25% vs 67% global). Higher disease burden occurred in countries with higher D614G frequencies (Egypt=98%, Morocco=90%, Tunisia=52%, South Africa) with D614G as the first confirmed case. V367F, D364Y, V483A and G476S mutations associated with efficient ACE2 receptor binding and severe disease were not observed in Africa. 95% of all RdRp mutations were deaminations leading to CpG depletion and possible attenuation of virulence. More genomic and experimental studies are needed to increase our understanding of the temporal evolution of the virus in Africa, clarify our findings, and reveal hot spots that may undermine successful therapeutic and vaccine interventions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.