UK COVID-19 transmission chains trace back to Spain, France and Italy

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A team of scientists analyzed the first wave of the Covid-19 epidemic in the UK.
Their analysis relies on virus genomic sequences> 50k – of which 26k were assembled by the COVID-19 Genomics UK (COG-UK) consortium – offering an unprecedented level of insight into the origins and behavior of the chains transmission since the start of the pandemic.

The COVID epidemic is exceptionally well represented by the genomic sampling of the virus Dr Erik Volz Author of the study

Comprehensive analysis, carried out by scientists at the universities of Oxford, Edinburgh and Imperial College London, published in Science, reveals that the virus was introduced into the UK well over a thousand times at the start of 2020 and the rate and source of introduction changed very quickly.

During this period, the greatest number of transmission chains were introduced from Spain (33%), France (29%), then Italy (12%) – with China accounting for only 0.4% of imports. The study shows how the UK national lockdown affected individual transmission chains.

Corresponding and co-principal author, Professor Oliver Pybus, of the Oxford Zoology Department and the Oxford Martin School, said: “This study shows that it is possible to accurately trace the transmission lines of viruses. individual in time and space. Carrying out weekly analyzes means that genomic monitoring can become a key part of public health surveillance ”.

Overview of new variants

The results provide crucial context for what is currently happening in the UK’s second wave, and the team helped identify the new variant (called B.1.1.7) growing rapidly in the UK. .

Scientists say that a detailed comparison of the behavior of the new variant with that of the first wave lines will be crucial to understanding why B.1.1.7 is spreading so quickly now.

Prior to the March 2020 lockdown, high travel volumes and few restrictions on international arrivals led to the establishment and co-circulation of over 1,000 identifiable transmission lines in the UK, jointly contributing to a accelerated epidemic growth which rapidly exceeded national contact tracing capacity.

Professor Pybus said: ‘By reconstructing where and when COVID-19 was introduced to the UK, we can see that previous travel and quarantine interventions could have helped reduce the acceleration and intensity of the first wave of cases in UK. ”

The team expects similar trends in other countries with relatively large epidemics and high international travel volumes.

While the UK’s national lockdown coincided with limited importation and a reduction in regional lineage diversity, its impact on lineage extinction depended on size, meaning that the largest and most widespread persisted through the summer.

Unparalleled views on the epidemic

The over-dispersed nature of SARS-CoV-2 transmission is likely to have promoted greater survival of larger and more widespread lineages and faster local elimination of lineages in low prevalence regions, underscoring the importance rapid or preventive interventions to reduce transmission.

The extent to which the surviving lines contributed to the ongoing UK epidemic in the fall and winter of 2020, including the effect of specific mutations on line growth rates, is currently under review. ‘study.

The structure and dynamics of transmission measured for the first time in this study provide a new context in which future public health actions at regional, national and international scales should be planned and evaluated.

Dr Erik Volz, author of the MRC Center for Global Infectious Disease Analysis study at Imperial College London, said: “The COVID epidemic is exceptionally well represented by genomic sampling of viruses. This allows scientists to keep track of new variants of the virus, as all viruses mutate, and informs our COVID-19 planning. ”

Co-lead author Louis du Plessis, Oxford Department of Zoology, said: “Our work offers unparalleled insights into what happens in an individual epidemic. The UK publicly shares large volumes of viral genetic data on a weekly basis and if you do not have this level of surveillance you will not know the real situation of the evolution and transmission of the virus.

Co-lead author Verity Hill, a doctoral student, based at the University of Edinburgh, said: “This kind of continuous, nationally coordinated genomic sequencing not only enables the high resolution analysis that we present, but also helps other countries to put their genomic data into context and help the global pandemic response ”.

The opportunity to step up large-scale genomic surveillance was made possible by the decision to fund the COVID-19 Genomics UK (COG-UK) consortium in April and builds on decades of basic research in the blue sky on the evolution of the virus, led by Oxford. and the universities of Edinburgh, which developed the theory that led scientists to have these tools and theories.

Adapted from a press release from the University of Oxford

/ Public publication. The content in this public version is from the original organization and may be ad hoc in nature, edited for clarity, style and length. See it in full here.

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