Emergence and Spread of SARS-CoV-2 Lineages B.1.1.7 and P.1 in Italy

Italy's second wave of SARS-CoV-2 has hit hard, with more than three million cases and over 100,000 deaths, representing an almost ten-fold increase in the numbers reported by August 2020. Herein, we present an analysis of 6515 SARS-CoV-2 sequences sampled in Italy between 29 January 2020 and 1 March 2021 and show how different lineages emerged multiple times independently despite lockdown restrictions. Virus lineage B.1.177 became the dominant variant in November 2020, when cases peaked at 40,000 a day, but since January 2021 this is being replaced by the B.1.1.7 'variant of concern'. In addition, we report a sudden increase in another documented variant of concern-lineage P.1-from December 2020 onwards, most likely caused by a single introduction into Italy. We again highlight how international importations drive the emergence of new lineages and that genome sequencing should remain a top priority for ongoing surveillance in Italy.

Automated summary

Italy's second wave of SARS-CoV-2 has caused significant impacts, with different virus lineages emerging independently multiple times despite lockdown measures. The dominant variant shifted from B.1.177 to the 'variant of concern' B.1.1.7 since January 2021. The sudden increase of lineage P.1 from December 2020 onwards was likely caused by a single introduction into Italy, emphasizing the importance of international importations in driving new lineages.