Long-Term Care the Most Common Site of Outbreaks of New Norovirus Strain

​From September through December 2012, 65% of acute gastroenteritis outbreaks involving the new norovirus strain GII.4 Sydney occurred in long-term care facilities, according to an article in the January 25, 2013, Morbidity and Mortality Weekly Report. The next most common site was restaurants, accounting for 13% of outbreaks with the new strain. Overall, GII.4 Sydney—which was first identified in Australia in March 2012—caused 53% of the 266 norovirus outbreaks reported from September through December 2012 via the Centers for Disease Control and Prevention's (CDC) laboratory surveillance network for reporting norovirus activity. The new strain has spread quickly nationwide; the proportion of outbreaks due to the new strain increased significantly from September through December. Of outbreaks involving the new strain, 51% resulted from direct person-to-person transmission, 20% were foodborne, 1% were waterborne, and 28% involved an unknown transmission mode.