Updated classification of norovirus genogroups and genotypes

Area of Science:

• Virology
• Molecular Biology
• Public Health

Background:

• Noroviruses are genetically diverse RNA viruses causing acute gastroenteritis in mammals.
• Existing classification schemes require updates due to the emergence of new norovirus strains.
• Phylogenetic classification relies on VP1 gene amino acid diversity (genotypes) and RdRp region nucleotide diversity (P-types).

Purpose of the Study:

• To update the phylogenetic classification of noroviruses based on recent sequence data.
• To expand the number of recognized norovirus genogroups and genotypes.
• To define tentative new genogroups and genotypes for viruses with limited sequence data.

Main Methods:

• Utilized the 2× standard deviation (sd) criteria for sequence clustering.
• Analyzed amino acid diversity of the complete VP1 gene for genogroup and genotype assignment.
• Analyzed nucleotide diversity of the RNA-dependent RNA polymerase (RdRp) region for P-type classification.

Main Results:

• Expanded norovirus genogroups to 10 (GI-GX) and genotypes to 48.
• Identified 9 GI, 27 GII, 3 GIII, 2 GIV, 2 GV, 2 GVI, and 1 each for GVII, GVIII, GIX, and GX genotypes.
• Classified viruses with single public sequences into tentative new genogroups (GNA1, GNA2) and genotypes (GII.NA1, GII.NA2, GIV.NA1).
• Defined 60 P-types (14 GI, 37 GII, 2 GIII, 1 GIV, 2 GV, 2 GVI, 1 GVII, 1 GX), 2 tentative P-groups, and 14 tentative P-types.

Conclusions:

• The updated classification accommodates newly reported noroviruses and expands the phylogenetic framework.
• Tentative classifications provide a provisional structure for novel viruses pending further data.
• Future updates will integrate complete genome sequences, coordinated by the international norovirus classification working group.