LAUSR

Background We describe the epidemiology of the first cases diagnosed in our institute of infections with the Beta variant and how this variant was imported to Marseille. Methods The SARS-CoV-2 Beta variant was identified based on analyses of sequences of viral genomes or of a spike gene fragment obtained by next-generation sequencing using Illumina technology, or a real-time reverse-transcription-PCR (qPCR) specific of the Beta variant. Results The first patient diagnosed as infected with the SARS-CoV-2 Beta variant was sampled on 15 January 2021. Twenty-nine patients were diagnosed in January 2021 (two weeks). Fifteen (52%) patients were of Comorian nationality. Eight (28%) had travelled abroad, including six who had returned from Comoros. Phylogeny based on SARS-CoV-2 genomes from 11 of these patients and their best BLAST hits from the GISAID database showed that seven patients, including the four returning from Comoros, were clustered with 27 other genomes from GISAID that included the six first Beta variant genomes described in Comoros in January 2021. Conclusions Our analyses highlight that, as for the case of other SARS-CoV-2 variants that have been diagnosed in Marseille, the Beta variant was imported to Marseille through travel from abroad. It had limited spread in our geographical area.