Human sapoviruses (SaVs) are a common cause of the acute gastroenteritis epidemic worldwide, and SaV outbreaks and infections have become more frequent in recent years. Since the end of December, 2015 to December, 2016, 2 gastroenteritis outbreaks occurred in 2 kindergarten classes (outbreaks A and B) in the Baoan district, Shenzhen, China. Feces and swabs were collected for laboratory tests of causative agents, and no bacterial pathogens were detected. Both the outbreaks were positive for SaV with a detection rate of 75% of symptomatic cases (6/8) in outbreak A and 71% (10/14) in outbreak B. For outbreak B, 1 of 3 asymptomatic teachers was detected to be SaV positive. The genome of some of the strains in this study was obtained, and the strains from outbreak A were genotyped into GII.3, while those from outbreak B were genotyped into GI.2, according to the phylogenetic analysis of the polymerase and the capsid region. No recombination was identified in either the GII.3 or GI.2 strain. GI.2 strains experience chronological variation, and the GI.2 strain in this study belonged to the most recent variant, which was observed from 2008 to 2016. The variation mainly occurred in the P domain from 1990 to 2016. Meanwhile, GII.3 strains shared greater similarity (>98.2%) at the amino acid identities; from 1999 to 2015, only 5 of them were in the predicted P domain. Our results suggest that it is necessary to conduct routine SaV surveillance and molecular characterization to further understand the SaV epidemic.

Background:During 2016-2017, the previously rare GII.P16-GII.2 norovirus suddenly emerged as the predominant genotype causing gastroenteritis outbreaks in China and other countries. Its origin, phylodynamics, and mechanism behind the predominance remain unclear.Methods:Bayesian phylogenetic analyses were performed on 180 full capsid and 150 polymerase sequences of 2016-2017 GII.P16-GII.2 noroviruses in China, and those for all publicly available GII.P16 and GII.2 sequences. Saliva-based histo-blood group antigen (HBGA) binding assays and crystal structural analysis were conducted by using the P proteins of 2016-2017 GII.P16-GII.2 noroviruses.Results:The reemerging GII.P16-GII.2 norovirus showed a rapid genetic diversification after its emergence in 2012-2013. The antigenicity and HBGA binding profile of the early 2016-2017 and pre-2016 GII.2 noroviruses were similar. A further variant with a single Val256Ile mutation and the conventionally orientated Asp382 in the VP1 protein showed an expanded HBGA-binding spectrum. Mutations on the surface of polymerase that could alter its function were seen, which may help to accelerate the VP1 gene evolution to 5.5 × 10-3 substitutions per site per year. This virus can be traced back to Pearl River Delta, China.Conclusions:Our findings provide new insights into GII.2 norovirus epidemics and highlight the necessity of enhanced global surveillance for potential epidemics of rare-genotype noroviruses.

Objective To investigate the molecular epidemiological characteristics of human astrovirus (HAstV) in adults with diarrhea in Beijing,China.Methods A total of 519 fecal specimens from patients ≥14 years of age with acute gastroenteritis were collected with relevant clinical data in Xuanwu Hospital Capital Medical University from August 2008 to July 2009.HAstV was detected by RT-PCR,positive PCR products were sequenced and phylogenetic analyses were carried out.Results The total positive rate of HAstV was 6.7％ (35/519),of which 15 were male,the positive rate was 5.6％ (15/270);the female was 20 cases,the positive rate was 8.0％ (20/249).There was no statistically significant difference (x2=1.26,P=0.261).The seasonal peak occurred in October (17.5％,14/80) and the highest detection rate was in the age group of≥ 60 (8.9％,7/79).Positive specimens were sequenced and 24 sequences were obtained.Phylogenetic analysis showed that seventeen (70.8％,17/24) strains were classic HAstV-1,four strains were HAstV-2,one strain was HAstV-4,one strain was HAstV-5 and one strain was HAstV-8.Conclusions HAstV is one of the important pathogens causing diarrhea in adults in Beijing and classic HAstV-1 is the predominant strain.

During October-December 2016, the number of norovirus outbreaks in China increased sharply from the same period during the previous 4 years. We identified a recombinant norovirus strain, GII. P16-GII.2, as the cause of 44 (79%) of the 56 outbreaks, signaling that this strain could replace the predominant GII. 4 viruses.