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. Author manuscript; available in PMC: 2014 Mar 17.
Published in final edited form as: Curr Opin Gastroenterol. 2014 Jan;30(1):25–33. doi: 10.1097/MOG.0000000000000022

FIGURE 1.

FIGURE 1

Phylogenetic analysis of noroviruses (NoVs). (a) NoVs are classified into genogroups and genotypes based on the amino acid sequence of the capsid protein VP1. Human NoVs belong to genogroups I, II and IV and some porcine viruses are also detected within GII (dotted circle). The predominant human NoV genotype described worldwide is GII.4 (highlighted in the grey box). New variants emerge every 2–3 years and replace the previously dominant GII.4 variant. (b) From the 1990s to 2013, seven different GII.4 variants have been associated with global epidemics of gastroenteritis. These include the US 1996/96 variant in 1996, the Farmington Hills variant in 2002, the Hunter variant in 2004, the 2006a, 2006b variants in 2007–08, the New Orleans variant from 2009 to 2012 and Sydney 2012 in late 2012. The timeline of emergence and circulation of predominant GII.4 variants is shown. The line above the variant name indicates when the variant emerged to when it was last detected.