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J Gen Virol. 2019 Oct;100(10):1393-1406. doi: 10.1099/jgv.0.001318.

Updated classification of norovirus genogroups and genotypes.

Author information

Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Department of Viroscience, Erasmus University Medical Center, Rotterdam, The Netherlands.
Division of Viral Products, Food and Drug Administration, Silver Spring, MD, USA.
Department of Microbiology, Stanley Ho Centre for Emerging Infectious Diseases and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, PR China.
Caliciviruses Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
Department of Veterinary Medicine, University of Bari Aldo Moro, Bari, Italy.
Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH, USA.
School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney 2052, Australia.
Laboratory of Viral infection I, Kitasato Institute for Life Sciences Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan.
Division for Virology, Centre for Infectious Diseases Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.


Noroviruses are genetically diverse RNA viruses associated with acute gastroenteritis in mammalian hosts. Phylogenetically, they can be segregated into different genogroups as well as P (polymerase)-groups and further into genotypes and P-types based on amino acid diversity of the complete VP1 gene and nucleotide diversity of the RNA-dependent RNA polymerase (RdRp) region of ORF1, respectively. In recent years, several new noroviruses have been reported that warrant an update of the existing classification scheme. Using previously described 2× standard deviation (sd) criteria to group sequences into separate clusters, we expanded the number of genogroups to 10 (GI-GX) and the number of genotypes to 49 (9 GI, 27 GII, 3 GIII, 2 GIV, 2 GV, 2 GVI and 1 genotype each for GVII, GVIII, GIX [formerly GII.15] and GX). Viruses for which currently only one sequence is available in public databases were classified into tentative new genogroups (GNA1 and GNA2) and genotypes (GII.NA1, GII.NA2 and GIV.NA1) with their definitive assignment awaiting additional related sequences. Based on nucleotide diversity in the RdRp region, noroviruses can be divided into 60 P-types (14 GI, 37 GII, 2 GIII, 1 GIV, 2 GV, 2 GVI, 1 GVII and 1 GX), 2 tentative P-groups and 14 tentative P-types. Future classification and nomenclature updates will be based on complete genome sequences and will be coordinated and disseminated by the international norovirus classification-working group.


2xSD criteria; Norovirus; P-group; P-type; acute gastroenteritis; classification; genogroup; genotype


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