Alpha variant spread via UK ‘superseeding’ event, researchers say

The rapid spread of the Alpha variant of COVID-19 results from biological changes in the virus and has been reinforced by large numbers of infected people “exporting” the variant to several parts of the UK, in what researchers are calling a ” super-seeding ”an event.

Results of the largest phylogeographic analysis ever, published today in the journal Science, maps the spread of the variant (also known as lineage B.1.1.7) from its origins in Kent and Greater London in November 2020 in all but five counties of Wales, Scotland, D Northern Ireland and England by January 19.

Dr Moritz Kraemer, lead author of the study and researcher Branco Weiss at the Oxford Department of Zoology, said: “In early December 2020, the epicenter of COVID-19 transmission in England rapidly shifted from the north -west and north-east in London. and the Southeast, as the Alpha variant took hold. As people traveled from London and the South East to other parts of the UK, they ‘seeded’ new transmission chains of the variant. This continued as national ‘superseeding’ event that only started to slow down in early January. Although travel was restricted, after travel restrictions were introduced on December 20, this was offset by exponential growth continues Alpha variant cases. “

The rapid spread of the Alpha variant across the UK led to initial reports that it could be up to 80% more transmissible than the original strain. This study, published today by researchers from universities such as Oxford, Northeastern and Edinburgh, shows that mobility has significantly affected its spread and early growth rates. According to the researchers, this highlights the need for epidemiologists to work closely with virologists and geneticists to quickly create accurate estimates of transmissibility for new variants.

Professor Oliver Pybus, Principal Investigator of the Oxford Martin Program on Pandemic Genomics, explains: “Estimates of the transmission advantage of Alpha over previous strains were initially 80%, but have declined over time. A first wave of exports of Alpha variants to places in England with low infection rates, since the massive outbreak in Kent and Greater London, explains why it first spread so quickly.

“The Alpha variant contains genetic modifications that make it more heritable. It is likely that the Alpha variant was 30-40% more transmissible than the original strain. And the first estimates were higher because we didn’t know how much it grew. was exacerbated.by human mobility and by the number of contacts that different groups of people have. Especially, as more and more variants emerge and spread to other countries of the world, we must take care to take into account account for these phenomena when evaluating the inherent transmissibility of new variants. “

Verity Hill, co-author and University of Edinburgh researcher, says: “The Alpha variant began to spread mainly in London and the South East, even during the November lockdown in England. Once this measure was lifted, it quickly spread across the country. , while human movements have increased dramatically. Our ability to trace the origins of the Alpha to a point source in South East England has important implications for how new variants appear and how they will spread across the UK. “

Dr Samuel V. Scarpino, principal investigator of the Network Science Institute at Northeastern University and the external faculty of the Santa Fe Institute, stresses the importance of integrative pathogen surveillance systems, “only by integrating genomics into high resolution, cases, tests and aggregated data. , anonymous mobility data has enabled us to identify the drivers of the emergence and spread of the Alpha variant in the UK.

“Uncovering the mechanisms behind the emergence of B.1.1.7 enables governments to respond more effectively and advances our scientific understanding of epidemics. The challenge now is to put in place similar surveillance systems globally. Fair and ethical data systems will be essential to end this pandemic and prevent future ones. “

Dr Kraemer concludes: “As new variants emerge, we expect them to spread significantly before travel restrictions are put in place, as has likely happened with the Delta variant. . Given the scale of its current outbreak, it probably looks like the UK is now a big country. exporter of the Delta variant to Europe and other parts of the world.

“The UK has decided to ease its restrictions because of our high vaccination rates and the certainty that we have protected the most vulnerable in society. But most of the rest have not. countries and the Delta variant could repeat this process elsewhere, underscoring the urgent need for faster and more equitable vaccine distribution around the world. ”