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Extensive global sampling and sequencing of the pandemic virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have enabled researchers to monitor its spread and to identify concerning new variants. Two important determinants of variant spread are how frequently they arise within individuals and how likely they are to be transmitted. To characterize within-host diversity and transmission, we deep-sequenced 1313 clinical samples from the United Kingdom. SARS-CoV-2 infections are characterized by low levels of within-host diversity when viral loads are high and by a narrow bottleneck at transmission. Most variants are either lost or occasionally fixed at the point of transmission, with minimal persistence of shared diversity, patterns that are readily observable on the phylogenetic tree. Our results suggest that transmission-enhancing and/or immune-escape SARS-CoV-2 variants are likely to arise infrequently but could spread rapidly if successfully transmitted.
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http://dx.doi.org/10.1126/science.abg0821 | DOI Listing |
Commun Med (Lond)
September 2025
Department of Microbiology and Immunology, Bio21 Institute and The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia.
Background: Mixed-species, mixed-strain plasmodia infections are known to occur in humans in malaria endemic areas. It may be surprising that to date, the extent of this complexity has not been systematically explored in high-burden countries of sub-Saharan Africa, especially in the reservoir of asymptomatic infections in all ages, which sustains transmission.
Methods: Here we take a metagenomic lens to these infections by sampling variable blood volumes from 188 afebrile residents living in high, seasonal transmission in Northern Sahelian Ghana.
FEMS Microbiol Ecol
September 2025
School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland, New Zealand, 1142.
The relationship between, and joint selection on, a host and its microbes-the holobiont-can impact evolutionary and ecological outcomes of the host and its microbial community. We develop an agent-based modelling framework for understanding the ecological dynamics of hosts and their microbiomes. Our model incorporates numerous microbial generations per host generation allowing selection on both host and microbes.
View Article and Find Full Text PDFThe evolutionary dynamics of seasonal influenza A viruses (IAVs) have been well characterized at the population level, with antigenic drift known to be a major force in driving strain turnover. The evolution of IAV populations at the within-host level, however, is still less well characterized. Improving our understanding of within-host IAV evolution has the potential to shed light on the source of new strains, including new antigenic variants, at the population level.
View Article and Find Full Text PDFUnlabelled: Metagenomics has become a powerful tool for studying microbial communities, allowing researchers to investigate microbial diversity within complex environmental samples. Recent advances in sequencing technology have enabled the recovery of near-complete microbial genomes directly from metagenomic samples, also known as metagenome-assembled genomes (MAGs). However, accurately characterizing these genomes remains a significant challenge due to the presence of sequencing errors, incomplete assembly, and contamination.
View Article and Find Full Text PDFPLoS Biol
September 2025
Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GeorgiaUnited States of America.
For many viruses, narrow bottlenecks acting during transmission sharply reduce genetic diversity in a recipient host relative to the donor. Since genetic diversity represents adaptive potential, such losses of diversity are thought to limit the opportunity for viral populations to undergo antigenic change and other adaptive processes. Thus, a detailed picture of evolutionary dynamics during transmission is critical to understanding the forces driving viral evolution at an epidemiologic scale.
View Article and Find Full Text PDF