Introduction and transmission of SARS-CoV-2 lineage B.1.1.7, Alpha variant, in Denmark
Posted on 2022-05-04 - 07:36
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.
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Michaelsen, Thomas Y.; Bennedbæk, Marc; Christiansen, Lasse E.; Jørgensen, Mia S. F.; Møller, Camilla H.; Sørensen, Emil A.; et al. (2022). Introduction and transmission of SARS-CoV-2 lineage B.1.1.7, Alpha variant, in Denmark. figshare. Collection. https://doi.org/10.6084/m9.figshare.c.5978621.v1
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AUTHORS (27)
TM
Thomas Y. Michaelsen
MB
Marc Bennedbæk
LC
Lasse E. Christiansen
MJ
Mia S. F. Jørgensen
CM
Camilla H. Møller
ES
Emil A. Sørensen
SK
Simon Knutsson
JB
Jakob Brandt
TJ
Thomas B. N. Jensen
CC
Clarisse Chiche-Lapierre
EC
Emilio F. Collados
TS
Trine Sørensen
CP
Celine Petersen
VL
Vang Le-Quy
MS
Mantas Sereika
FH
Frederik T. Hansen
MR
Morten Rasmussen
JF
Jannik Fonager
SK
Søren M. Karst
RM
Rasmus L. Marvig
KEYWORDS
sustain epidemic controlphylogenetic analyses revealeddetailed travel history2 genomes generated19 genome consortiumsubstantial early expansionbalanced travel restrictionscases directly linked7 genomes collectedisolation procedures coupleddenmark abstract background2 lineage b7 february 2021comprehensive surveillance effortsearly 2021unchanged restrictionssequencing efforts7 casespositive cases7 relativethroughput sequencingstudy highlightsstill unmonitoredscaled phylogenyrepresenting 34relative numberquality bnovember 2020introductions variedincreased bemerging variantsdanish covidcomprehensive setcase numbersalpha variant