Findings from the surveillance focusing on viral loads of norovirus GII. 4 have been released elsewhere5, 55. previously much less vulnerable to GII. 4 variants; therefore , the global spread of GII. 17 Kawasaki 2014 needs to be monitored. Norovirus GII. 4 continues to be predominating in viral gastroenteritis for 20 years. Here the authors report the emergence and predominance of a novel fast-evolving GII. 17 lineage norovirus causing viral gastroenteritis in Hong AS-252424 Kong, with a shift in age group distribution of affected individuals towards an older age group as compared to GII. 4. Human being norovirus, from the genusNorovirusand familyCaliciviridae, is the leading cause of acute gastroenteritis worldwide1. Genetically, this computer virus is classified into at least 6 genogroups and nearly forty genotypes based on viral protein 1 (VP1) sequences2. Despite the broad genetic diversity, one genotype, known as genogroup II genotype 4 (GII. 4), has been the major circulating genotype in community and health-care settings since 1996 with periodic emergence of novel GII. 4 variants every 24 years3. Norovirus GII. 4 AS-252424 infections are associated with more severe clinical manifestations and hospitalization4. Our earlier hospital-based study also indicated that GII. 4 accounted for nearly 90% of hospitalized norovirus gastroenteritis that represents the severe end of the spectrum of disease5. Despite the overwhelmingly predominance of norovirus GII. 4 strains in the past two decades, studies on historical stool specimens dated back to the 1970s and 1980s suggested that non-GII. 4 norovirus such as GII. 3 was commonly detected, at least in hospitalized paediatric diarrhoeal cases6. This raises the possibility that epidemic norovirus may not be limited only to the GII. 4 genotype. Notably, accumulating evidence suggests that the circulation of different norovirus genotypes is highly dynamic, probably due to herd immunity7. In late 2014, we notice a rapid increase in the number of hospitalized norovirus gastroenteritis attributed to the emergent GII. 17 Kawasaki 2014 in Hong Kong. Here, we report epidemiological and virological characterization of norovirus GII. 17 cases. Our findings suggest close monitoring of the global spread of this emergent GII. 17 Kawasaki 2014 is necessary. == Results == == High norovirus GII. 17 activity during 20142015 winter == A total of 415 laboratory-confirmed hospitalized norovirus cases were studied in our ongoing local norovirus surveillance between March 2014 and May 2015, inclusively. The median age of patients was 6 years (interquartile range (IQR): 158 years). The male-to-female ratio was 1 . 14. Typical winter seasonality with higher norovirus activity in winter months (December 2014 to March 2015) AS-252424 was noticed (Fig. 1a). Norovirus genotype was successfully identified in 372 (89. 6%) cases. During the inter-seasonal period (March 2014November 2014), the predominant circulating norovirus genotype was GII. 4 (all but 2 belonged to the Sydney 2012) that accounted for 69. 2% (128/185) of genotyped cases; GII. 17 cases were only rarely (3. AS-252424 8%; 7/185) detected (Fig. 1a). A rapid rise in the number and proportion of GII. 17 cases was observed in winter months during which GII. 17 cases predominated over GII. 4 cases (65. 9% (110/167) versus 18. 6% (31/167); P <0. 0001, Fisher's exact test; Fig. 1a). Overall, the three most common norovirus genotypes detected during the report period were GII. 4 (43. 8%; n=163), GII. 17 (34. 4%; n=128) and GII. 6 (8. 9%; n=33). == Figure 1 . High activity of norovirus GII. 17 during the 20142015 winter in Hong Kong. == (a) Temporal distribution of hospitalized norovirus GII. 4 and GII. 17 cases during the study period from March 2014 to May 2015. Black arrow denotes first detection (27 September 2014) of the novel GII. 17 Kawasaki 2014. (b) Age group distribution of norovirus GII. 4 (n=163) Rabbit polyclonal to STAT1 and GII. 17 (n=128) cases. Red horizontal lines and crimson rectangular shades indicate medians and interquartile ranges, respectively. ****P <0. 0001 (MannWhitneyU-test). == Wide age distribution of norovirus GII. 17 infections == The median (IQR) age of GII. 17 (n=128) cases was significantly older than that of GII. 4 (n=163) cases (49 (975) versus 1 (18) years; P <0. 0001, MannWhitneyU-test; Fig. 1b). By age group, the proportion of children (aged <5 years), older children and young adults (aged 565 years) and older adults (aged > 65 years) in.