Nine additional complete genome sequences of HCV genotype 6 from Vietnam including new subtypes 6xb and 6xc

•We characterized nine full-length genomes of HCV-6 in Ho Chi Minh City, Vietnam.•They may represent six new subtype candidates beyond the assigned 24: 6a-6xa.•Co-analysis of sequences in ORF length indicates the existence of 20 such lineages.•Further analysis of the references in the NS5B region identified additional 22.•Following the eXtended format, we assigned two new subtypes, 6xb and 6xc.

We completely sequenced nine HCV-6 variants from Vietnam. They are grouped into six lineages beyond the 24 assigned subtypes, 6a-6xa, and 14 unclassified lineages that have been recently described with full-length genomes. Co-analysis with reference sequences in the NS5B region identified additional 22 such lineages, which made the total taxonomic number of HCV-6 increased to 66 that might be recognized at the subtype level. Because two of these six lineages revealed in this study each had >3 epidemiologically unlinked isolates identified, we proposed to assign them new subtypes 6xb and 6xc in following the eXtended format recently recommended in the expanded HCV nomenclature.