Norovirus GII.4 viruses have caused most gastroenteric infections for >2 decades, and new variants have emerged every 2–4 years since 2002 ( 7). Six pandemic GII.4 variants have been named after the place of first reported sequence and year of predominance: US 95–96, Farmington Hills 2002, Hunter 2004, Den Haag 2006, New Orleans 2009, and Sydney 2012. Several norovirus vaccine candidates are in preclinical studies and clinical trials ( 8); however, it is currently unclear if these vaccine formulations could protect against newly emerging GII.4 viruses that are often associated with more norovirus outbreaks and hospitalizations. Norovirus surveillance networks, such as NoroNet, CaliciNet U.S. and CaliciNet China, are tracking norovirus genotypes ( 11). Surveillance data from NoroNet has shown that GII.4 variants can be detected at low levels years before they cause a new pandemic (