An overview of SARS-CoV-2 variants circulating in the 2020-2022 period in Lombardy

Since the beginning of the pandemic, SARS-CoV-2 has shown genetic variability. All the variants that have sustained pandemic waves have shown several mutations, especially in the Spike protein that could affect viral pathogenesis. A total of 15,729 respiratory samples, collected between December 2020 and August 2022, have been included in this study. We report the circulation of SARS-CoV-2 variants in the Lombardy region, Italy, in a 2-year study period. Alpha, Delta, and Omicron variants became predominant causing the majority of cases whereas Beta or Gamma variants mostly caused local outbreaks. Next-generation sequenc-ing revealed several mutations and few deletions in all of the main variants. For example, 147 mutations were observed in the Spike protein of Omicron sublineages; 20% of these mutations occurred in the recep-tor-binding domain region. (c) 2023 Elsevier Inc. All rights reserved.

Automated summary

This study reports the circulation of SARS-CoV-2 variants in the Lombardy region, Italy, over a 2-year period. Alpha, Delta, and Omicron variants became predominant, causing the majority of cases, while Beta or Gamma variants mostly caused local outbreaks. Multiple mutations were observed in the Spike protein of each variant.