Updated classification and nomenclature of GII.4 and GII.17 norovirus variants

Preeti Chhabra, Centers for Disease Control and Prevention

Miranda de Graaf2, Vito Martella3, Peter A. White4, Janet Mans5, Kazuhiko Katayama6, Qiuhong Wang7, Kim Green8, Marion P.G. Koopmans2, Jan Vinjé1, on behalf of the Norovirus Classification Working Group. 1Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA, 2Department of Viroscience, Erasmus University Medical Center, Rotterdam, Netherlands, 3Department of Veterinary Medicine, University of Bari Aldo Moro, Bari, Italy, 4School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney 2052, Australia, 5Department of Medical Virology, University of Pretoria, South Africa, 6Laboratory of Virology, Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan, 7Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH, USA, 8Caliciviruses Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.

Molecular Epidemiology & Evolution

Norovirus genogroup I and II viruses account for the majority of infections in humans. Among these, GII.4 Sydney viruses have been the most frequently detected genotype worldwide since 2012—except during the 2014/15 season, when GII.17 viruses predominated in several East Asian countries. In recent years, several phylogenetically distinct emerging GII.4 sub-clusters, as well as a surge of GII.17 viruses have been reported. Using previously described criteria to classify noroviruses, we analyzed VP1 amino acid sequences from all publicly available GII.4 viruses and classified them into at least 14 (8 epidemic and 6 non-epidemic) GII.4 variants. They include GII.4 before 1995, GII.4 US95-96, GII.4 Henry, GII.4 Farmington Hills_2002, GII.4 Asia_2003, GII.4 Hunter_2004, GII.4 Yerseke_2006, GII.4 Den Haag_2006, GII.4 Osaka_2007, GII.4 New Orleans_2009, GII.4 Sydney_2012, GII.4 Hong Kong_2019, GII.4 San Francisco_2017 and GII.4 Wichita_2021. In addition, the new GII.4 Allegany_2018 cluster represents the first long sequence branch detected on at least 3 continents (North America, Africa and Australia). However, because detections of this cluster are currently limited and its evolutionary origin lies within the larger GII.4 Sydney cluster, we propose assigning it a tentative status until it evolves into an epidemic variant. GII.17 strains can be divided into 5 variant types including GII.17 French Guiana (previously cluster A), GII.17 Houston (cluster B), GII.17 Taipei (cluster C), GII.17 Kawasaki (Cluster D) and GII.17 Romania (new cluster). To ensure consistent classification and nomenclature of new emerging noroviruses, future updates will be coordinated and shared in collaboration with the Norovirus Classification Working Group.