Norovirus) cause diarrhea in humans and animals (1) (2) (3) . The NoV genome is 7.3-7.7 kb long with 3 open reading frames (ORFs) encoding a polyprotein that undergoes protease processing to produce several nonstructural proteins, including an RNA-dependent RNA polymerase (RdRp), a major capsid protein (VP1, capsid), and a minor capsid protein (VP2) (1, 4, 5) . The capsid protein contains a conserved shell (S) and hypervariable protruding (P) domains (6) . Noroviruses are genetically diverse and make up 27 genotypes within 5 genogroups, GI/1-8, GII/1-17, GIII/1-2, GIV, and GV, based on the capsid genes of 164 strains (7) . Human NoVs cause an estimated 23 million cases of illness annually in the United States (8) and >90% of nonbacterial epidemic gastroenteritis worldwide (1) . The low infectious dose, environmental resistance, strain diversity, shedding from asymptomatic persons, and varied transmission vehicles render human NoVs highly contagious.