For the past two decades, the majority of norovirus outbreaks have been caused by strains within the genogroup II, genotype 4 (GII.4 strains) subcluster. Between 1995 and 2006, four major norovirus pandemics associated with GII.4 strains were characterized using molecular epidemiologic methods. During the mid-1990's [24] strain US95/96 was responsible for ,55% of the norovirus outbreaks in the USA and 85% of the outbreaks in the Netherlands [25] . In 2002, the US95/96 strain was replaced by the Farmington Hills strain [26] , which was associated with ,80% of norovirus outbreaks [27] in the USA. In 2004, the Hunter GII.4 variant was detected in Australia, Europe, and Asia [28] [29] [30] . Hunter strains were largely replaced in 2006 by two new cocirculating GII.4 variants in the USA and Europe, Laurens (2006a) and Minerva (2006b) [5, 29, 31] . Although similar to Minerva, Apeldoorn317 (GII.4.2008, GenBank accession no. AB445395) represents a new evolutionary cluster in the phylogeny of the GII.4 viruses. Most recently, a new GII. 4.2006 4. variant, GII.4.2009 New Orleans, has been the predominate outbreak strain, although GII.4.2006 Minerva continues to circulate at low levels [1, 32] .