We report a norovirus GIV outbreak in the United States, 15 years after the last reported outbreak. During May 2016 in Wisconsin, 53 persons, including 4 food handlers, reported being ill. The outbreak was linked to individually prepared fruit consumed as a fruit salad. The virus was phylogenetically classified as a novel GIV genotype.
Norovirus is the leading cause of epidemic and endemic acute gastroenteritis globally. The virus can be transmitted through person-to-person contact, consumption of fecally contaminated food or water, or self-contamination after touching contaminated environmental surfaces (1,2). Noroviruses are divided into at least 10 genogroups (G), and viruses in GI, GII, GIV, GVIII, and GIX cause illness in humans (3). More than 99% of all norovirus outbreaks are caused by GI and GII viruses in the United States (4). GVIII includes 2 strains that have been detected in Japan during 2004 and 2011 (3), and GIX has caused 11 reported outbreaks in the United States since 2013 (https://www.cdc.gov/norovirus/reporting/calicinet/data.html).
GIV is divided into 2 recognized genotypes: GIV.1, which infects humans (5), and GIV.2, which infects canines and felines (6). GIV viruses were reported in humans in the Netherlands during 1998 and the United States during 1999 (7,8) and have since been sporadically reported in clinical and environmental samples (5,9–11). An outbreak linked to a GIV norovirus in the United States has not been reported since 2001 (4,8). In this article, we describe a 2016 foodborne norovirus outbreak associated with a novel GIV strain (tentatively GIV.NA).