Clinical relevance and genotypes of circulating noroviruses in northern Taiwan, 2006-2011

The incidence of noroviral gastroenteritis has increased dramatically in recent years, and norovirus (NoV) genogroup II.4 (GII.4) is associated with outbreaks worldwide. The NoV genotypes and their clinical relevance in children hospitalized with acute gastroenteritis between 2006 and 2011 in northern Taiwan were evaluated in this study. NoV sequences were amplified from 47 clinical specimens and phylogenetic analysis was performed. Based on noroviral capsid protein (VP1) and RNA dependent RNA polymerase (RdRp) phylogeny, circulating NoV could be divided into GII.2, GII.3, GII.12, and GII.4 and GII.16, GII.12, GII.g, and GII.4; respectively. The GII.4 subtype was predominant and could be divided further into the 2004 (Hunter), 2006b, and 2010 (New Orleans) subtypes. Regarding clinical manifestations, convulsive disorder occurred only in cases caused by NoV GII.4 2006b. Patients affected by NoV GII.4 2006b presented with a higher frequency of diarrhea (P=0.0204), longer duration of diarrhea (P=0.0215), more frequent hypoglycemia (P=0.038), and electrolyte imbalance (P=0.0487) than acute gastroenteritis caused by NoV GII.4 2010. Structural analysis showed that the amino acid changes in viral VP1 between GII.4 2006b and 2010 subtype were located mainly in the protruding domain 2 (P2 domain). In conclusion, the NoV GII.4 variants 2006b and 2010 were the main causes of acute gastroenteritis in hospitalized children in northern Taiwan during 2006-2011. The clinical presentations and structural changes in VP1 of the two NoV GII.4 variants should be evaluated in the future.