The study was done by Division of Systems Virology, Institute of Medical Science, University of Tokyo, Japan.
Newly emerging SARS-CoV-2 variants need to be carefully monitored for a potential increase in transmissibility, pathogenicity and resistance to the vaccine-induced immunity and antiviral drugs.
The emergence of a new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, Omicron, is the most urgent concern in the global health in December 2021 (ref. ). Our statistical modelling estimates that Omicron is >3.0-fold and >5.6-fold more transmissible than Delta in South Africa and the UK, respectively.
Intriguingly, cell culture experiments show that Omicron is less fusogenic than Delta and ancestral SARS-CoV-2. Although the spike (S) protein of Delta is efficiently cleaved into the two subunits, which facilitates cell-cell fusion2, Omicron S is faintly cleaved. Further, in hamster model, Omicron poorly infects and spreads in the lung and is less pathogenic compared to Delta and ancestral SARS-CoV-2. Our data suggest that the efficacy of SARS-CoV-2 S cleavage and viral fusogenicity are closely associated with viral pathogenicity, and Omicron evolved to exhibit increased transmissibility and attenuated pathogenicity.
The study was done by Division of Systems Virology, Institute of Medical Science, University of Tokyo, Japan. G2P-Japan Consortium.