The 1st molecular data uploaded to the international molecular surveillance database NoroNet from Australia, France, New Zealand, and Japan indicate that this increase is associated with emergence of a new variant of genotype II.4 (GII.4). The 1st report of this variant was from Australia in March 2012 (personal communication P.A. White, September 2012), and the strain sequence was submitted to GenBank (accession number: JX459908.1). In the United States (US), the variant (named Sydney 2012) was detected in September 2012 in five of 22 (23 percent) laboratory-confirmed outbreaks, and in November in 37 of 71 (52 percent) laboratory-confirmed outbreaks (recorded in the US norovirus surveillance network CaliciNet) . In 2 European countries that have not reported any indications of increased activity, the new variant has been found in outbreaks, 2 in Belgium (September and December 2012) and one in Denmark (November 2012). Other countries participating in NoroNet have not yet reported the new variant.