Background: Based on the impact public health of norovirus and the current progress in norovirus vaccine development, it is necessary to continuously monitor the epidemiology of norovirus infection, especially in children who are more susceptible to norovirus.
Objectives: To monitor the activity and genotypes of norovirus infection in sporadic diarrhea in Shanghainese children during 2014-2018.
Study design: Acute diarrheal cases were prospectively enrolled in the outpatient setting. Real-time reverse transcription-polymerase chain reaction was used for screening norovirus GI and GII genogroups. Dual norovirus genotypes were identified based on the partial capsid and polymerase gene sequences.
Results: Of the 3422 children with diarrhea, 510 (14.9%) were positive for noroviruses with 13 (2.5%) strains being GI genogroup and 497 (97.5%) strains being GII genogroup. Five distinct capsid GII genotypes were identified, including GII.4-Sydney/2012 (71.8%), GII.3 (13.8%), GII.17 (7.8%), GII.2 (6.0%), GII.6 (0.3%) and GII.8 (0.3%). Seven polymerase GII genotypes were identified, including GII.Pe (77.0%), GII.P12 (11.0%), GII.P17 (9.0%), GII.P16 (2.1%), and GII.P7, GII.P8 and GII.P2 in each (0.3%). Eleven distinct polymerase/capsid genotypes were identified with GII.Pe/GII.4-Sydney/2012 (74.2%), GII.P12/GII.3 (11.7%) and GII.P17/GII.17 (7.7%) being common. GII.P17/GII.17 strains were detected since September 2014. Recombinant GII.P16/GII.2 strains were detected since December 2016.
Conclusions: Norovirus is a major pathogen causing diarrhea in Shanghainese children. GII.Pe/GII.4-Sydney/2012 strains remained the predominant genotype. The emergence of GII.P17/GII.17 and GII.P16/GII.2 strains in sporadic diarrhea was consistent with norovirus-associated outbreaks attributable to these 2 novel variants in China. Continuous monitoring norovirus genotypes circulating in pediatric population is needed for current vaccine development.