OPEN medRxiv : the preprint server for health sciences | 4 Dec 2020
EB Hodcroft, M Zuber, S Nadeau, KHD Crawford, JD Bloom, D Veesler, TG Vaughan, I Comas, FG Candelas, T Stadler and RA Neher
Following its emergence in late 2019, SARS-CoV-2 has caused a global pandemic resulting in unprecedented efforts to reduce transmission and develop therapies and vaccines (WHO Emergency Committee, 2020; Zhu et al ., 2020). Rapidly generated viral genome sequences have allowed the spread of the virus to be tracked via phylogenetic analysis (Hadfield et al ., 2018; Pybus et al ., 2020; Worobey et al ., 2020). While the virus spread globally in early 2020 before borders closed, intercontinental travel has since been greatly reduced, allowing continent-specific variants to emerge. However, within Europe travel resumed in the summer of 2020, and the impact of this travel on the epidemic is not well understood. Here we report on a novel SARS-CoV-2 variant, 20A.EU1, that emerged in Spain in early summer, and subsequently spread to multiple locations in Europe, accounting for the majority of sequences by autumn. We find no evidence of increased transmissibility of this variant, but instead demonstrate how rising incidence in Spain, resumption of travel across Europe, and lack of effective screening and containment may explain the variant’s success. Despite travel restrictions and quarantine requirements, we estimate 20A.EU1 was introduced hundreds of times to countries across Europe by summertime travellers, likely undermining local efforts to keep SARS-CoV-2 cases low. Our results demonstrate how genomic surveillance is critical to understanding how travel can impact SARS-CoV-2 transmission, and thus for informing future containment strategies as travel resumes.
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