Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Division of Systems Virology, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Faculty of Medicine, Kobe University, Kobe, Japan.
Department of Cancer Pathology, Faculty of Medicine, Hokkaido University, Sapporo, Japan.
Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan.
Division of Molecular Pathobiology, International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan.
Division of International Research Promotion, International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan.
One Health Research Center, Hokkaido University, Sapporo, Japan.
Division of Molecular Virology and Genetics, Joint Research Center for Human Retrovirus infection, Kumamoto University, Kumamoto, Japan.
Department of Clinical Pathology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt.
Graduate School of Medicine, The University of Tokyo, 1130033, Tokyo, Japan.
Laboratory of Systems Virology, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan.
Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
International Collaboration Unit, International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan.
Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Institute for Genetic Medicine, Hokkaido University, Sapporo, Japan.
Tokyo Metropolitan Institute of Public Health, Tokyo, Japan.
One Health Research Center, Hokkaido University, Sapporo, Japan. matsuk@czc.hokudai.ac.jp.
International Collaboration Unit, International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan. matsuk@czc.hokudai.ac.jp.
Division of Risk Analysis and Management, International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan. matsuk@czc.hokudai.ac.jp.
Department of Cancer Pathology, Faculty of Medicine, Hokkaido University, Sapporo, Japan. tanaka@med.hokudai.ac.jp.
Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan. tanaka@med.hokudai.ac.jp.
Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan. fukut@pop.med.hokudai.ac.jp.
Division of Systems Virology, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan. KeiSato@g.ecc.u-tokyo.ac.jp.
Graduate School of Medicine, The University of Tokyo, 1130033, Tokyo, Japan. KeiSato@g.ecc.u-tokyo.ac.jp.
CREST, Japan Science and Technology Agency, Saitama, Japan. KeiSato@g.ecc.u-tokyo.ac.jp.
The emergence of a new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, Omicron, is an urgent global health concern (ref.1). Our statistical modelling suggests that Omicron has spread more rapidly than the Delta variant in several countries including South Africa. Cell culture experiments show that Omicron is less fusogenic than Delta and an ancestral SARS-CoV-2 strain. Although the spike (S) protein of Delta is efficiently cleaved into two subunits, which facilitates cell-cell fusion2,3, Omicron S is less efficiently cleaved compared to Delta S and ancestral SARS-CoV-2 S. Furthermore, in a hamster model, Omicron shows decreased lung infectivity and is less pathogenic compared to Delta and ancestral SARS-CoV-2.