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Introduction and transmission of SARS-CoV-2 lineage B.1.1.7, Alpha variant, in Denmark

2022; BioMed Central; Volume: 14; Issue: 1 Linguagem: Inglês

10.1186/s13073-022-01045-7

1756-994X

Thomas Yssing Michaelsen, Marc Bennedbæk, Lasse Engbo Christiansen, Mia S. F. Jørgensen, Camilla Holten Møller, Emil A. Sørensen, Simon Knutsson, Jakob Brandt, Thomas Bygh Nymann Jensen, Clarisse Chiche-Lapierre, Emilio F. Collados, Trine Sørensen, Celine Petersen, Vang Quy Le, Mantas Sereika, Frederik T. Hansen, Morten Rasmussen, Jannik Fonager, Søren Michael Karst, Rasmus L. Marvig, Marc Stegger, Raphael N. Sieber, Robert Skov, Rebecca Legarth, Tyra Grove Krause, Anders Fomsgaard, Kasper Skytte Andersen, Martin Hjorth Andersen, Amalie Berg, Susanne R. Bielidt, Sebastian Mølvang Dall, Erika Dvarionaite, Susan Hove Hansen, Vibeke Børsholt Rudkjøbing, Rasmus Hansen Kirkegaard, Wagma Saei, Trine B. Nicolajsen, Stine Karstenskov Østergaard, Rasmus Froberg Brøndum, Martin Bøgsted, Katja Hose, Tomer Sagi, Miroslaw Pakanec, David Fuglsang-Damgaard, Mette Mølvadgaard, Henrik Krarup, Christina Wiid Svarrer, Mette T. Christiansen, Anna Cäcilia Ingham, Thor Bech Johannesen, Martín Basterrechea, Berit Lilje, Kirsten Ellegaard, Povilas Matusevicius, Lars Christoffersen, Man-Hung Eric Tang, Kim Lee Ng, Sofie Marie Edslev, Sharmin Baig, Ole H. Larsen, Kristian Alsbjerg Skipper, Søren Vang, Kurt Handberg, Marc T. K. Nielsen, Carl M. Kobel, Camilla Andersen, Irene Harder Tarpgaard, Svend Ellermann‐Eriksen, José Alfredo Samaniego Castruita, Uffe Vest Schneider, Nana G. Jacobsen, Christian Østergaard Andersen, Martin Schou Pedersen, Kristian Schønning, Nikolai Kirkby, Lene Nielsen, Line Nilsson, Martin Barfred Friis, Thomas Sundelin, Thomas Arn Hansen, Marianne Nielsine Skov, Thomas Vognbjerg Sydenham, Xiaohui Chen Nielsen, Christian Højte Schouw, Anders Møller Jensen, Ea S. Marmolin, John Coia, Dorte Terp Andersen, Mads Albertsen,

Animal Virus Infections Studies

Abstract Background In early 2021, the SARS-CoV-2 lineage B.1.1.7 (Alpha variant) became dominant across large parts of the world. In Denmark, comprehensive and real-time test, contact-tracing, and sequencing efforts were applied to sustain epidemic control. Here, we use these data to investigate the transmissibility, introduction, and onward transmission of B.1.1.7 in Denmark. Methods We analyzed a comprehensive set of 60,178 SARS-CoV-2 genomes generated from high-throughput sequencing by the Danish COVID-19 Genome Consortium, representing 34% of all positive cases in the period 14 November 2020 to 7 February 2021. We calculated the transmissibility of B.1.1.7 relative to other lineages using Poisson regression. Including all 1976 high-quality B.1.1.7 genomes collected in the study period, we constructed a time-scaled phylogeny, which was coupled with detailed travel history and register data to outline the introduction and onward transmission of B.1.1.7 in Denmark. Results In a period with unchanged restrictions, we estimated an increased B.1.1.7 transmissibility of 58% (95% CI: [56%, 60%]) relative to other lineages. Epidemiological and phylogenetic analyses revealed that 37% of B.1.1.7 cases were related to the initial introduction in November 2020. The relative number of cases directly linked to introductions varied between 10 and 50% throughout the study period. Conclusions Our findings corroborate early estimates of increased transmissibility of B.1.1.7. Both substantial early expansion when B.1.1.7 was still unmonitored and continuous foreign introductions contributed considerably to case numbers. Finally, our study highlights the benefit of balanced travel restrictions and self-isolation procedures coupled with comprehensive surveillance efforts, to sustain epidemic control in the face of emerging variants.