Detection of GII.4 Sydney 2012 Norovirus in Ireland

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In late 2012, a significant increase in norovirus associated outbreaks was identified in Ireland, a trend also noted in numerous countries across the northern hemisphere.  Genogroup II genotype 4 (GII.4) has been the dominant strain of norovirus detected worldwide and in Ireland since 2002. However, norovirus evolves rapidly and since the mid 1990’s, new genetic variants of GII.4 have emerged and become the predominant strain on average every two to three years.

A new genetic variant of GII.4, termed Sydney 2012, was identified in association with the recent increase in norovirus outbreaks in Europe.  As part of the surveillance of norovirus outbreaks, a selection of specimens from Irish outbreaks, undergo genetic characterisation at the National Virus Reference Laboratory. Sequence and phylogenetic analysis have identified the GII.4 Sydney 2012 variant circulating across Ireland in late 2012.